/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2026 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_internal.h"

#if defined(SDL_PLATFORM_WINDOWS) && !defined(SDL_PLATFORM_CYGWIN)
#include "../core/windows/SDL_windows.h"
#else
#include <unistd.h>
#endif

#ifdef HAVE_STDIO_H
#include <stdio.h>
#include <errno.h>
#include <sys/stat.h>
#endif
#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif

#ifdef SDL_PLATFORM_APPLE
#include <fcntl.h>
#endif

#include "SDL_iostream_c.h"


/* This file provides a general interface for SDL to read and write
   data sources.  It can easily be extended to files, memory, etc.
*/

// IOStreams have various Properties. The first time SDL_GetIOProperties() is
//  called, it creates the SDL_PropertiesID and then uses this function
//  interface to fill in the appropriate props for the stream on-demand.
typedef void (*SetIOPropertiesFn)(SDL_PropertiesID props, void *userdata);

struct SDL_IOStream
{
    SDL_IOStreamInterface iface;
    void *userdata;
    SetIOPropertiesFn setioprops;
    SDL_IOStatus status;
    SDL_PropertiesID props;
};

#ifdef SDL_PLATFORM_3DS
#include "n3ds/SDL_iostreamromfs.h"
#endif // SDL_PLATFORM_3DS

#ifdef SDL_PLATFORM_ANDROID
#include <unistd.h>
#include "../core/android/SDL_android.h"
#endif

#if defined(SDL_PLATFORM_WINDOWS) && !defined(SDL_PLATFORM_CYGWIN)

typedef struct IOStreamWindowsData
{
    HANDLE h;
    void *data;
    size_t size;
    size_t left;
    void *write_data;
    size_t write_pos;
    bool writable;
    bool append;
    bool autoclose;
} IOStreamWindowsData;


// Functions to read/write Win32 API file pointers
#ifndef INVALID_SET_FILE_POINTER
#define INVALID_SET_FILE_POINTER 0xFFFFFFFF
#endif

#define READAHEAD_BUFFER_SIZE   1024
#define WRITEBEHIND_BUFFER_SIZE 1024

static HANDLE SDLCALL windows_file_open(const char *filename, const char *mode)
{
#if !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
    UINT old_error_mode;
#endif
    HANDLE h;
    DWORD r_right, w_right;
    DWORD must_exist, truncate;
    int a_mode;

    // "r" = reading, file must exist
    // "w" = writing, truncate existing, file may not exist
    // "wx"= writing, file must not exist
    // "r+"= reading or writing, file must exist
    // "a" = writing, append file may not exist
    // "a+"= append + read, file may not exist
    // "w+" = read, write, truncate. file may not exist
    // "w+x"= read, write, file must not exist

    must_exist = (SDL_strchr(mode, 'r') != NULL) ? OPEN_EXISTING : 0;
    truncate = (SDL_strchr(mode, 'w') != NULL) ? CREATE_ALWAYS : 0;
    r_right = (SDL_strchr(mode, '+') != NULL || must_exist) ? GENERIC_READ : 0;
    a_mode = (SDL_strchr(mode, 'a') != NULL) ? OPEN_ALWAYS : 0;
    w_right = (a_mode || SDL_strchr(mode, '+') || truncate) ? GENERIC_WRITE : 0;

    if (truncate && (SDL_strchr(mode, 'x') != NULL)) {
        truncate = CREATE_NEW;
    }

    if (!r_right && !w_right) {
        return INVALID_HANDLE_VALUE; // inconsistent mode
    }
    // failed (invalid call)

#if !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
    // Do not open a dialog box if failure
    old_error_mode = SetErrorMode(SEM_NOOPENFILEERRORBOX | SEM_FAILCRITICALERRORS);
#endif

    {
        LPWSTR str = WIN_UTF8ToStringW(filename);
        h = CreateFileW(str,
                       (w_right | r_right),
                       (w_right) ? 0 : FILE_SHARE_READ,
                       NULL,
                       (must_exist | truncate | a_mode),
                       FILE_ATTRIBUTE_NORMAL,
                       NULL);
        SDL_free(str);
    }

#if !defined(SDL_PLATFORM_XBOXONE) && !defined(SDL_PLATFORM_XBOXSERIES)
    // restore old behavior
    SetErrorMode(old_error_mode);
#endif

    if (h == INVALID_HANDLE_VALUE) {
        char *error;
        if (SDL_asprintf(&error, "Couldn't open %s", filename) > 0) {
            WIN_SetError(error);
            SDL_free(error);
        } else {
            SDL_SetError("Couldn't open %s", filename);
        }
    }
    return h;
}

static bool windows_flush_write_buffer(IOStreamWindowsData *iodata,
                                        SDL_IOStatus *status)
{
    if (iodata->write_pos == 0) {
        return true;  // Nothing to flush
    }

    // In append mode, seek to EOF before writing
    if (iodata->append) {
        LARGE_INTEGER windowsoffset;
        windowsoffset.QuadPart = 0;
        if (!SetFilePointerEx(iodata->h, windowsoffset,
                              &windowsoffset, FILE_END)) {
            if (status) {
                *status = SDL_IO_STATUS_ERROR;
            }
            WIN_SetError("Error seeking in datastream");
            return false;
        }
    }

    DWORD bytes;
    if (!WriteFile(iodata->h, iodata->write_data,
                   (DWORD)iodata->write_pos, &bytes, NULL)) {
        if (status) {
            *status = SDL_IO_STATUS_ERROR;
        }
        WIN_SetError("Error writing to datastream");
        return false;
    }

    iodata->write_pos = 0;
    return true;
}

static Sint64 SDLCALL windows_file_size(void *userdata)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *) userdata;
    LARGE_INTEGER size;

    if (!GetFileSizeEx(iodata->h, &size)) {
        return WIN_SetError("windows_file_size");
    }

    return size.QuadPart;
}

static Sint64 SDLCALL windows_file_seek(void *userdata, Sint64 offset, SDL_IOWhence whence)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *) userdata;
    DWORD windowswhence;
    LARGE_INTEGER windowsoffset;

    if (!windows_flush_write_buffer(iodata, NULL)) {
        return -1;
    }

    // FIXME: We may be able to satisfy the seek within buffered data
    if ((whence == SDL_IO_SEEK_CUR) && (iodata->left)) {
        offset -= iodata->left;
    }
    iodata->left = 0;

    switch (whence) {
    case SDL_IO_SEEK_SET:
        windowswhence = FILE_BEGIN;
        break;
    case SDL_IO_SEEK_CUR:
        windowswhence = FILE_CURRENT;
        break;
    case SDL_IO_SEEK_END:
        windowswhence = FILE_END;
        break;
    default:
        SDL_SetError("windows_file_seek: Unknown value for 'whence'");
        return -1;
    }

    windowsoffset.QuadPart = offset;
    if (!SetFilePointerEx(iodata->h, windowsoffset, &windowsoffset, windowswhence)) {
        return WIN_SetError("Error seeking in datastream");
    }
    return windowsoffset.QuadPart;
}

static size_t SDLCALL windows_file_read(void *userdata, void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *) userdata;
    size_t total_need = size;
    size_t total_read = 0;
    size_t read_ahead;
    DWORD bytes;

    if (!windows_flush_write_buffer(iodata, status)) {
        return 0;
    }

    if (iodata->left > 0) {
        void *data = (char *)iodata->data +
                     iodata->size -
                     iodata->left;
        read_ahead = SDL_min(total_need, iodata->left);
        SDL_memcpy(ptr, data, read_ahead);
        iodata->left -= read_ahead;

        if (read_ahead == total_need) {
            return size;
        }
        ptr = (char *)ptr + read_ahead;
        total_need -= read_ahead;
        total_read += read_ahead;
    }

    if (total_need < READAHEAD_BUFFER_SIZE) {
        if (!ReadFile(iodata->h, iodata->data, READAHEAD_BUFFER_SIZE, &bytes, NULL)) {
            DWORD error = GetLastError();
            switch (error) {
            case ERROR_BROKEN_PIPE:
                *status = SDL_IO_STATUS_EOF;
                break;
            case ERROR_NO_DATA:
                *status = SDL_IO_STATUS_NOT_READY;
                break;
            default:
                *status = SDL_IO_STATUS_ERROR;
                WIN_SetError("Error reading from datastream");
                break;
            }
            return 0;  // !!! FIXME: this should return the bytes read from any readahead we finished out before this (the `iodata->left > 0` code above). In that case, fail on the next read.
        } else if (bytes == 0) {
            *status = SDL_IO_STATUS_EOF;
        }
        read_ahead = SDL_min(total_need, bytes);
        SDL_memcpy(ptr, iodata->data, read_ahead);
        iodata->size = bytes;
        iodata->left = bytes - read_ahead;
        total_read += read_ahead;
    } else {
        if (!ReadFile(iodata->h, ptr, (DWORD)total_need, &bytes, NULL)) {
            DWORD error = GetLastError();
            switch (error) {
            case ERROR_BROKEN_PIPE:
                *status = SDL_IO_STATUS_EOF;
                break;
            case ERROR_NO_DATA:
                *status = SDL_IO_STATUS_NOT_READY;
                break;
            default:
                *status = SDL_IO_STATUS_ERROR;
                WIN_SetError("Error reading from datastream");
                break;
            }
            return 0;  // !!! FIXME: this should return the bytes read from any readahead we finished out before this (the `iodata->left > 0` code above). In that case, fail on the next read.
        } else if (bytes == 0) {
            *status = SDL_IO_STATUS_EOF;
        }
        total_read += bytes;
    }
    return total_read;
}

static size_t SDLCALL windows_file_write(void *userdata, const void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *)userdata;
    const Uint8 *src = (const Uint8 *)ptr;
    size_t remaining = size;
    size_t total_written = 0;

    if (!iodata->writable) {
        *status = SDL_IO_STATUS_READONLY;
        return 0;
    }

    // Invalidate read-ahead buffer if it has data
    if (iodata->left) {
        if (!SetFilePointer(iodata->h, -(LONG)iodata->left,
                            NULL, FILE_CURRENT)) {
            *status = SDL_IO_STATUS_ERROR;
            WIN_SetError("Error seeking in datastream");
            return 0;
        }
        iodata->left = 0;
    }

    // For large writes, flush buffer and write directly
    if (size >= WRITEBEHIND_BUFFER_SIZE) {
        if (!windows_flush_write_buffer(iodata, status)) {
            return 0;
        }

        // In append mode, seek to EOF before direct write
        if (iodata->append) {
            LARGE_INTEGER windowsoffset;
            windowsoffset.QuadPart = 0;
            if (!SetFilePointerEx(iodata->h, windowsoffset,
                                  &windowsoffset, FILE_END)) {
                *status = SDL_IO_STATUS_ERROR;
                WIN_SetError("Error seeking in datastream");
                return 0;
            }
        }

        DWORD bytes;
        if (!WriteFile(iodata->h, ptr, (DWORD)size, &bytes, NULL)) {
            *status = SDL_IO_STATUS_ERROR;
            WIN_SetError("Error writing to datastream");
            return 0;
        } else if (bytes == 0 && size > 0) {
            *status = SDL_IO_STATUS_NOT_READY;
        }
        return bytes;
    }

    // Buffer small writes
    while (remaining > 0) {
        size_t space = WRITEBEHIND_BUFFER_SIZE - iodata->write_pos;
        size_t to_buffer = SDL_min(remaining, space);

        SDL_memcpy((char *)iodata->write_data + iodata->write_pos,
                   src, to_buffer);
        iodata->write_pos += to_buffer;
        src += to_buffer;
        remaining -= to_buffer;
        total_written += to_buffer;

        if (iodata->write_pos == WRITEBEHIND_BUFFER_SIZE) {
            if (!windows_flush_write_buffer(iodata, status)) {
                return total_written;
            }
        }
    }

    return total_written;
}

static bool SDLCALL windows_file_flush(void *userdata, SDL_IOStatus *status)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *)userdata;

    if (!windows_flush_write_buffer(iodata, status)) {
        return false;
    }

    // Sync to disk
    if (!FlushFileBuffers(iodata->h)) {
        return WIN_SetError("Error flushing datastream");
    }
    return true;
}

static bool SDLCALL windows_file_close(void *userdata)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *)userdata;
    bool result = true;

    if (!windows_flush_write_buffer(iodata, NULL)) {
        result = false;
    }

    if (iodata->h != INVALID_HANDLE_VALUE) {
        if (iodata->autoclose) {
            CloseHandle(iodata->h);
        }
        iodata->h = INVALID_HANDLE_VALUE;
    }
    SDL_free(iodata->data);
    SDL_free(iodata->write_data);
    SDL_free(iodata);
    return result;
}

static void windows_setioprops(SDL_PropertiesID props, void *userdata)
{
    const IOStreamWindowsData *iodata = (const IOStreamWindowsData *) userdata;
    SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_WINDOWS_HANDLE_POINTER, iodata->h);
}

SDL_IOStream *SDL_IOFromHandle(HANDLE handle, const char *mode, bool autoclose)
{
    IOStreamWindowsData *iodata = (IOStreamWindowsData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        if (autoclose) {
            CloseHandle(handle);
        }
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    if (GetFileType(handle) == FILE_TYPE_DISK) {
        iface.size = windows_file_size;
        iface.seek = windows_file_seek;
    }
    iface.read = windows_file_read;
    iface.write = windows_file_write;
    iface.flush = windows_file_flush;
    iface.close = windows_file_close;

    iodata->h = handle;
    iodata->writable = (SDL_strchr(mode, 'w') != NULL) ||
                       (SDL_strchr(mode, 'a') != NULL) ||
                       (SDL_strchr(mode, '+') != NULL);
    iodata->append = (SDL_strchr(mode, 'a') != NULL);
    iodata->autoclose = autoclose;

    iodata->data = (char *)SDL_malloc(READAHEAD_BUFFER_SIZE);
    if (!iodata->data) {
        iface.close(iodata);
        return NULL;
    }

    iodata->write_data = (char *)SDL_malloc(WRITEBEHIND_BUFFER_SIZE);
    if (!iodata->write_data) {
        iface.close(iodata);
        return NULL;
    }
    iodata->write_pos = 0;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        iface.close(iodata);
    } else {
        iostr->setioprops = windows_setioprops;
    }

    return iostr;
}
#else

// Functions to read/write file descriptors. Not used for windows.

typedef struct IOStreamFDData
{
    int fd;
    bool autoclose;
} IOStreamFDData;

static int SDL_fdatasync(int fd)
{
    int result = 0;

#if defined(SDL_PLATFORM_APPLE)  // Apple doesn't have fdatasync (rather, the symbol exists as an incompatible system call).
    result = fcntl(fd, F_FULLFSYNC);
#elif defined(SDL_PLATFORM_HAIKU)
    result = fsync(fd);
#elif defined(HAVE_FDATASYNC)
    result = fdatasync(fd);
#endif
    return result;
}

static Sint64 SDLCALL fd_seek(void *userdata, Sint64 offset, SDL_IOWhence whence)
{
    IOStreamFDData *iodata = (IOStreamFDData *) userdata;
    int fdwhence;

    switch (whence) {
    case SDL_IO_SEEK_SET:
        fdwhence = SEEK_SET;
        break;
    case SDL_IO_SEEK_CUR:
        fdwhence = SEEK_CUR;
        break;
    case SDL_IO_SEEK_END:
        fdwhence = SEEK_END;
        break;
    default:
        SDL_SetError("Unknown value for 'whence'");
        return -1;
    }

    off_t result = lseek(iodata->fd, (off_t)offset, fdwhence);
    if (result < 0) {
        SDL_SetError("Couldn't get stream offset: %s", strerror(errno));
    }
    return result;
}

static size_t SDLCALL fd_read(void *userdata, void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamFDData *iodata = (IOStreamFDData *) userdata;
    ssize_t bytes;
    do {
        bytes = read(iodata->fd, ptr, size);
    } while ((bytes < 0) && (errno == EINTR));

    ssize_t result = bytes;
    if ((bytes > 0) && (bytes < size)) {   // was it a short read, EOF, or error?
        // try to read the difference, so we can rule out a short read.
        do {
            result = read(iodata->fd, ((Uint8 *) ptr) + bytes, size - bytes);
        } while ((result < 0) && (errno == EINTR));

        if (result > 0) {
            bytes += result;
            result = bytes;
            SDL_assert(bytes <= size);
        }
    }

    if (result < 0) {
        if (errno == EAGAIN) {
            *status = SDL_IO_STATUS_NOT_READY;
        } else {
            *status = SDL_IO_STATUS_ERROR;
            SDL_SetError("Error reading from datastream: %s", strerror(errno));
        }
        if (bytes < 0) {
            bytes = 0;
        }
    } else if (result == 0) {
        *status = SDL_IO_STATUS_EOF;
    } else if (result < size) {
        *status = SDL_IO_STATUS_NOT_READY;
    }
    return (size_t)bytes;
}

static size_t SDLCALL fd_write(void *userdata, const void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamFDData *iodata = (IOStreamFDData *) userdata;
    ssize_t bytes;
    do {
        bytes = write(iodata->fd, ptr, size);
    } while ((bytes < 0) && (errno == EINTR));

    ssize_t result = bytes;
    if ((bytes > 0) && (bytes < size)) {   // was it a short write, or error?
        // try to write the difference, so we can rule out a short read.
        do {
            result = write(iodata->fd, ((Uint8 *) ptr) + bytes, size - bytes);
        } while ((result < 0) && (errno == EINTR));

        if (result > 0) {
            bytes += result;
            result = bytes;
            SDL_assert(bytes <= size);
        }
    }

    if (result < 0) {
        if (errno == EAGAIN) {
            *status = SDL_IO_STATUS_NOT_READY;
        } else {
            *status = SDL_IO_STATUS_ERROR;
            SDL_SetError("Error writing to datastream: %s", strerror(errno));
        }
        if (bytes < 0) {
            bytes = 0;
        }
    } else if (result < size) {
        *status = SDL_IO_STATUS_NOT_READY;
    }

    return (size_t)bytes;
}

static bool SDLCALL fd_flush(void *userdata, SDL_IOStatus *status)
{
    IOStreamFDData *iodata = (IOStreamFDData *) userdata;
    int result;
    do {
        result = SDL_fdatasync(iodata->fd);
    } while (result < 0 && errno == EINTR);

    // We get EINVAL when flushing a pipe, just make that a no-op
    if (result < 0 && errno != EINVAL) {
        return SDL_SetError("Error flushing datastream: %s", strerror(errno));
    }
    return true;
}

static bool SDLCALL fd_close(void *userdata)
{
    IOStreamFDData *iodata = (IOStreamFDData *) userdata;
    bool status = true;
    if (iodata->autoclose) {
        if (close(iodata->fd) < 0) {
            status = SDL_SetError("Error closing datastream: %s", strerror(errno));
        }
    }
    SDL_free(iodata);
    return status;
}

static void fd_setioprops(SDL_PropertiesID props, void *userdata)
{
    const IOStreamFDData *iodata = (const IOStreamFDData *) userdata;
    SDL_SetNumberProperty(props, SDL_PROP_IOSTREAM_FILE_DESCRIPTOR_NUMBER, iodata->fd);
}

SDL_IOStream *SDL_IOFromFD(int fd, bool autoclose)
{
    IOStreamFDData *iodata = (IOStreamFDData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        if (autoclose) {
           close(fd);
        }
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    // There's no fd_size because SDL_GetIOSize emulates it the same way we'd do it for fd anyhow.
    iface.seek = fd_seek;
    iface.read = fd_read;
    iface.write = fd_write;
    iface.flush = fd_flush;
    iface.close = fd_close;

    iodata->fd = fd;
    iodata->autoclose = autoclose;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        iface.close(iodata);
    } else {
        iostr->setioprops = fd_setioprops;
    }

    return iostr;
}
#endif // SDL_PLATFORM_WINDOWS && !SDL_PLATFORM_CYGWIN

#if defined(HAVE_STDIO_H) && !(defined(SDL_PLATFORM_WINDOWS) && !defined(SDL_PLATFORM_CYGWIN))

// Functions to read/write stdio file pointers. Not used for windows.

typedef struct IOStreamStdioData
{
    FILE *fp;
    bool autoclose;
} IOStreamStdioData;

#ifdef HAVE_FOPEN64
#define fopen fopen64
#endif
#ifdef HAVE_FSEEKO64
#define fseek_off_t off64_t
#define fseek       fseeko64
#define ftell       ftello64
#elif defined(HAVE_FSEEKO)
#if defined(OFF_MIN) && defined(OFF_MAX)
#define FSEEK_OFF_MIN OFF_MIN
#define FSEEK_OFF_MAX OFF_MAX
#elif defined(HAVE_LIMITS_H)
/* POSIX doesn't specify the minimum and maximum macros for off_t so
 * we have to improvise and dance around implementation-defined
 * behavior. This may fail if the off_t type has padding bits or
 * is not a two's-complement representation. The compilers will detect
 * and eliminate the dead code if off_t has 64 bits.
 */
#define FSEEK_OFF_MAX (((((off_t)1 << (sizeof(off_t) * CHAR_BIT - 2)) - 1) << 1) + 1)
#define FSEEK_OFF_MIN (-(FSEEK_OFF_MAX)-1)
#endif
#define fseek_off_t off_t
#define fseek       fseeko
#define ftell       ftello
#elif defined(HAVE__FSEEKI64)
#define fseek_off_t __int64
#define fseek       _fseeki64
#define ftell       _ftelli64
#else
#ifdef HAVE_LIMITS_H
#define FSEEK_OFF_MIN LONG_MIN
#define FSEEK_OFF_MAX LONG_MAX
#endif
#define fseek_off_t long
#endif

static Sint64 SDLCALL stdio_seek(void *userdata, Sint64 offset, SDL_IOWhence whence)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) userdata;
    int stdiowhence;

    switch (whence) {
    case SDL_IO_SEEK_SET:
        stdiowhence = SEEK_SET;
        break;
    case SDL_IO_SEEK_CUR:
        stdiowhence = SEEK_CUR;
        break;
    case SDL_IO_SEEK_END:
        stdiowhence = SEEK_END;
        break;
    default:
        SDL_SetError("Unknown value for 'whence'");
        return -1;
    }

#if defined(FSEEK_OFF_MIN) && defined(FSEEK_OFF_MAX)
    if (offset < (Sint64)(FSEEK_OFF_MIN) || offset > (Sint64)(FSEEK_OFF_MAX)) {
        SDL_SetError("Seek offset out of range");
        return -1;
    }
#endif

    // don't make a possibly-costly API call for the noop seek from SDL_TellIO
    const bool is_noop = (whence == SDL_IO_SEEK_CUR) && (offset == 0);

    if (is_noop || fseek(iodata->fp, (fseek_off_t)offset, stdiowhence) == 0) {
        const Sint64 pos = ftell(iodata->fp);
        if (pos < 0) {
            SDL_SetError("Couldn't get stream offset: %s", strerror(errno));
            return -1;
        }
        return pos;
    }
    SDL_SetError("Error seeking in datastream: %s", strerror(errno));
    return -1;
}

static size_t SDLCALL stdio_read(void *userdata, void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) userdata;
    const size_t bytes = fread(ptr, 1, size, iodata->fp);
    if (bytes < size) {
        if (ferror(iodata->fp)) {
            if (errno == EAGAIN) {
                *status = SDL_IO_STATUS_NOT_READY;
                clearerr(iodata->fp);
            } else {
                *status = SDL_IO_STATUS_ERROR;
                SDL_SetError("Error reading from datastream: %s", strerror(errno));
            }
        } else {
            SDL_assert(feof(iodata->fp));
            *status = SDL_IO_STATUS_EOF;
        }
    }
    return bytes;
}

static size_t SDLCALL stdio_write(void *userdata, const void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) userdata;
    const size_t bytes = fwrite(ptr, 1, size, iodata->fp);
    if (bytes == 0 && ferror(iodata->fp)) {
        if (errno == EAGAIN) {
            *status = SDL_IO_STATUS_NOT_READY;
            clearerr(iodata->fp);
        } else {
            *status = SDL_IO_STATUS_ERROR;
            SDL_SetError("Error writing to datastream: %s", strerror(errno));
        }
    }
    return bytes;
}

static bool SDLCALL stdio_flush(void *userdata, SDL_IOStatus *status)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) userdata;
    if (fflush(iodata->fp) != 0) {
        if (errno == EAGAIN) {
            *status = SDL_IO_STATUS_NOT_READY;
            return false;
        } else {
            return SDL_SetError("Error flushing datastream: %s", strerror(errno));
        }
    }

    int result;
    int fd = fileno(iodata->fp);
    do {
        result = SDL_fdatasync(fd);
    } while (result < 0 && errno == EINTR);

    if (result < 0) {
        return SDL_SetError("Error flushing datastream: %s", strerror(errno));
    }
    return true;
}

static bool SDLCALL stdio_close(void *userdata)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) userdata;
    bool status = true;
    if (iodata->autoclose) {
        if (fclose(iodata->fp) != 0) {
            status = SDL_SetError("Error closing datastream: %s", strerror(errno));
        }
    }
    SDL_free(iodata);
    return status;
}

static void stdio_setioprops(SDL_PropertiesID props, void *userdata)
{
    const IOStreamStdioData *iodata = (const IOStreamStdioData *) userdata;
    FILE *fp = iodata->fp;
    SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_STDIO_FILE_POINTER, fp);
    SDL_SetNumberProperty(props, SDL_PROP_IOSTREAM_FILE_DESCRIPTOR_NUMBER, fileno(fp));
}

SDL_IOStream *SDL_IOFromFP(FILE *fp, bool autoclose)
{
    IOStreamStdioData *iodata = (IOStreamStdioData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        if (autoclose) {
           fclose(fp);
        }
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    // There's no stdio_size because SDL_GetIOSize emulates it the same way we'd do it for stdio anyhow.
    iface.seek = stdio_seek;
    iface.read = stdio_read;
    iface.write = stdio_write;
    iface.flush = stdio_flush;
    iface.close = stdio_close;

    iodata->fp = fp;
    iodata->autoclose = autoclose;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        iface.close(iodata);
    } else {
        iostr->setioprops = stdio_setioprops;
    }

    return iostr;
}
#endif // HAVE_STDIO_H && !SDL_PLATFORM_WINDOWS && !SDL_PLATFORM_CYGWIN

// Functions to read/write memory pointers

typedef struct IOStreamMemData
{
    Uint8 *base;
    Uint8 *here;
    Uint8 *stop;
    size_t size;
    SDL_PropertiesID props;
} IOStreamMemData;

static Sint64 SDLCALL mem_size(void *userdata)
{
    const IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    return (iodata->stop - iodata->base);
}

static Sint64 SDLCALL mem_seek(void *userdata, Sint64 offset, SDL_IOWhence whence)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    Uint8 *newpos;

    switch (whence) {
    case SDL_IO_SEEK_SET:
        newpos = iodata->base + offset;
        break;
    case SDL_IO_SEEK_CUR:
        newpos = iodata->here + offset;
        break;
    case SDL_IO_SEEK_END:
        newpos = iodata->stop + offset;
        break;
    default:
        SDL_SetError("Unknown value for 'whence'");
        return -1;
    }
    if (newpos < iodata->base) {
        newpos = iodata->base;
    }
    if (newpos > iodata->stop) {
        newpos = iodata->stop;
    }
    iodata->here = newpos;
    return (Sint64)(iodata->here - iodata->base);
}

static size_t mem_io(void *userdata, void *dst, const void *src, size_t size)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    const size_t mem_available = (iodata->stop - iodata->here);
    if (size > mem_available) {
        size = mem_available;
    }
    SDL_memcpy(dst, src, size);
    iodata->here += size;
    return size;
}

static size_t SDLCALL mem_read(void *userdata, void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    const size_t retval = mem_io(userdata, ptr, iodata->here, size);
    if ((retval < size) && (iodata->stop == iodata->here)) {
        *status = SDL_IO_STATUS_EOF;
    }
    return retval;
}

static size_t SDLCALL mem_write(void *userdata, const void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    const size_t retval = mem_io(userdata, iodata->here, ptr, size);
    if ((retval < size) && (iodata->stop == iodata->here)) {
        SDL_SetError("Memory buffer is full");
        *status = SDL_IO_STATUS_ERROR;
    }
    return retval;
}

static bool SDLCALL mem_close(void *userdata)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    SDL_free_func free_func = SDL_GetPointerProperty(iodata->props, SDL_PROP_IOSTREAM_MEMORY_FREE_FUNC_POINTER, NULL);
    if (free_func) {
        free_func(iodata->base);
    }
    SDL_free(userdata);
    return true;
}

static void mem_setioprops(SDL_PropertiesID props, void *userdata)
{
    IOStreamMemData *iodata = (IOStreamMemData *) userdata;
    SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_MEMORY_POINTER, iodata->base);
    SDL_SetNumberProperty(props, SDL_PROP_IOSTREAM_MEMORY_SIZE_NUMBER, iodata->size);
    SDL_assert(iodata->props == 0);
    iodata->props = props;
}

// Functions to create SDL_IOStream structures from various data sources

// private platforms might define SKIP_STDIO_DIR_TEST in their build configs, too.
#if (defined(SDL_PLATFORM_WINDOWS) && !defined(SDL_PLATFORM_CYGWIN)) || defined(SDL_PLATFORM_EMSCRIPTEN)
#define SKIP_STDIO_DIR_TEST 1
#endif

#if defined(HAVE_STDIO_H) && !defined(SKIP_STDIO_DIR_TEST)
static bool IsStdioFileADirectory(FILE *f)
{
    struct stat st;
    return ((fstat(fileno(f), &st) == 0) && (S_ISDIR(st.st_mode)));
}
#else
#define IsStdioFileADirectory(f) false
#endif

#ifdef SDL_PLATFORM_ANDROID
static void android_setioprops(SDL_PropertiesID props, void *userdata)
{
    SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_ANDROID_AASSET_POINTER, userdata);
}
#endif

SDL_IOStream *SDL_IOFromFile(const char *file, const char *mode)
{
    SDL_IOStream *iostr = NULL;

    CHECK_PARAM(!file || !*file) {
        SDL_InvalidParamError("file");
        return NULL;
    }
    CHECK_PARAM(!mode || !*mode) {
        SDL_InvalidParamError("mode");
        return NULL;
    }

#ifdef SDL_PLATFORM_ANDROID
#ifdef HAVE_STDIO_H
    // Try to open the file on the filesystem first
    if (*file == '/') {
        FILE *fp = fopen(file, mode);
        if (fp) {
            if (IsStdioFileADirectory(fp)) {
                fclose(fp);
                SDL_SetError("%s is a directory", file);
                return NULL;
            }
            return SDL_IOFromFP(fp, true);
        }
    } else if (SDL_strncmp(file, "content://", 10) == 0) {
        // Try opening content:// URI
        int fd = Android_JNI_OpenFileDescriptor(file, mode);
        if (fd == -1) {
            // SDL error is already set.
            return NULL;
        }

        FILE *fp = fdopen(fd, mode);
        if (!fp) {
            close(fd);
            SDL_SetError("Unable to open file descriptor (%d) from URI %s: %s", fd, file, strerror(errno));
            return NULL;
        }

        return SDL_IOFromFP(fp, true);
    } else if (SDL_strncmp(file, "assets://", 9) != 0) {
        // Try opening it from internal storage if it's a relative path
        char *path = NULL;
        SDL_asprintf(&path, "%s/%s", SDL_GetAndroidInternalStoragePath(), file);
        if (path) {
            FILE *fp = fopen(path, mode);
            SDL_free(path);
            if (fp) {
                if (IsStdioFileADirectory(fp)) {
                    fclose(fp);
                    SDL_SetError("%s is a directory", path);
                    return NULL;
                }
                return SDL_IOFromFP(fp, true);
            }
        }
    }
#endif // HAVE_STDIO_H

    // Try to open the file from the asset system?
    void *iodata = NULL;
    if (!Android_JNI_FileOpen(&iodata, file, mode)) {
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    iface.size = Android_JNI_FileSize;
    iface.seek = Android_JNI_FileSeek;
    iface.read = Android_JNI_FileRead;
    iface.write = Android_JNI_FileWrite;
    iface.close = Android_JNI_FileClose;

    iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        iface.close(iodata);
    } else {
        iostr->setioprops = android_setioprops;
    }

#elif defined(SDL_PLATFORM_IOS)

    // Try to open the file on the filesystem first
    FILE *fp = NULL;
    if (*file == '/') {
        fp = fopen(file, mode);
    } else {
        // We can't write to the current directory, so use a writable path
        char *base = SDL_GetPrefPath("", "");
        if (!base) {
            return NULL;
        }

        char *path = NULL;
        SDL_asprintf(&path, "%s%s", base, file);
        SDL_free(base);
        if (!path) {
            return NULL;
        }

        fp = fopen(path, mode);
        SDL_free(path);

        if (!fp) {
            fp = fopen(file, mode);
        }
    }

    if (!fp) {
        SDL_SetError("Couldn't open %s: %s", file, strerror(errno));
    } else if (IsStdioFileADirectory(fp)) {
        fclose(fp);
        SDL_SetError("%s is a directory", file);
    } else {
        iostr = SDL_IOFromFP(fp, true);
    }

#elif defined(SDL_PLATFORM_WINDOWS) && !defined(SDL_PLATFORM_CYGWIN)
    HANDLE handle = windows_file_open(file, mode);
    if (handle != INVALID_HANDLE_VALUE) {
        iostr = SDL_IOFromHandle(handle, mode, true);
    }

#elif defined(HAVE_STDIO_H)
    {
        #if defined(SDL_PLATFORM_3DS)
        FILE *fp = N3DS_FileOpen(file, mode);
        #else
        FILE *fp = fopen(file, mode);
        #endif

        if (!fp) {
            SDL_SetError("Couldn't open %s: %s", file, strerror(errno));
        } else if (IsStdioFileADirectory(fp)) {
            fclose(fp);
            SDL_SetError("%s is a directory", file);
        } else {
            iostr = SDL_IOFromFP(fp, true);
        }
    }

#else
    SDL_SetError("SDL not compiled with stdio support");
#endif // SDL_PLATFORM_ANDROID

    return iostr;
}

SDL_IOStream *SDL_IOFromMem(void *mem, size_t size)
{
    CHECK_PARAM(size && !mem) {
        SDL_InvalidParamError("mem");
        return NULL;
    }

    IOStreamMemData *iodata = (IOStreamMemData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    iface.size = mem_size;
    iface.seek = mem_seek;
    iface.read = mem_read;
    iface.write = mem_write;
    iface.close = mem_close;

    iodata->base = (Uint8 *)mem;
    iodata->here = iodata->base;
    iodata->stop = iodata->base + size;
    iodata->size = size;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        SDL_free(iodata);
    } else {
        iostr->setioprops = mem_setioprops;
    }

    return iostr;
}

SDL_IOStream *SDL_IOFromConstMem(const void *mem, size_t size)
{
    CHECK_PARAM(size && !mem) {
        SDL_InvalidParamError("mem");
        return NULL;
    }

    IOStreamMemData *iodata = (IOStreamMemData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    iface.size = mem_size;
    iface.seek = mem_seek;
    iface.read = mem_read;
    // leave iface.write as NULL.
    iface.close = mem_close;

    iodata->base = (Uint8 *)mem;
    iodata->here = iodata->base;
    iodata->stop = iodata->base + size;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        SDL_free(iodata);
    } else {
        iostr->setioprops = mem_setioprops;
    }

    return iostr;
}

typedef struct IOStreamDynamicMemData
{
    SDL_PropertiesID props;
    IOStreamMemData data;
    Uint8 *end;
} IOStreamDynamicMemData;

static Sint64 SDLCALL dynamic_mem_size(void *userdata)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    return mem_size(&iodata->data);
}

static Sint64 SDLCALL dynamic_mem_seek(void *userdata, Sint64 offset, SDL_IOWhence whence)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    return mem_seek(&iodata->data, offset, whence);
}

static size_t SDLCALL dynamic_mem_read(void *userdata, void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    const size_t retval = mem_io(&iodata->data, ptr, iodata->data.here, size);
    if ((retval < size) && (iodata->data.stop == iodata->data.here)) {
        *status = SDL_IO_STATUS_EOF;
    }
    return retval;
}

static bool dynamic_mem_realloc(IOStreamDynamicMemData *iodata, size_t size)
{
    size_t chunksize = (size_t)SDL_GetNumberProperty(iodata->props, SDL_PROP_IOSTREAM_DYNAMIC_CHUNKSIZE_NUMBER, 1024);
    if (!chunksize) {
        chunksize = 1024;
    }

    // We're intentionally allocating more memory than needed so it can be null terminated
    size_t chunks = (((iodata->end - iodata->data.base) + size) / chunksize) + 1;
    size_t length = (chunks * chunksize);
    Uint8 *base = (Uint8 *)SDL_realloc(iodata->data.base, length);
    if (!base) {
        return false;
    }

    size_t here_offset = (iodata->data.here - iodata->data.base);
    size_t stop_offset = (iodata->data.stop - iodata->data.base);
    iodata->data.base = base;
    iodata->data.here = base + here_offset;
    iodata->data.stop = base + stop_offset;
    iodata->end = base + length;
    return iodata->props ? SDL_SetPointerProperty(iodata->props, SDL_PROP_IOSTREAM_DYNAMIC_MEMORY_POINTER, base) : true;
}

static size_t SDLCALL dynamic_mem_write(void *userdata, const void *ptr, size_t size, SDL_IOStatus *status)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    if (size > (size_t)(iodata->data.stop - iodata->data.here)) {
        if (size > (size_t)(iodata->end - iodata->data.here)) {
            if (!dynamic_mem_realloc(iodata, size)) {
                *status = SDL_IO_STATUS_ERROR;
                return 0;
            }
        }
        iodata->data.stop = iodata->data.here + size;
    }
    const size_t retval = mem_io(&iodata->data, iodata->data.here, ptr, size);
    SDL_assert(retval == size);  // we should have allocated enough to cover this!
    return retval;
}

static bool SDLCALL dynamic_mem_close(void *userdata)
{
    const IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    void *mem = iodata->props ? SDL_GetPointerProperty(iodata->props, SDL_PROP_IOSTREAM_DYNAMIC_MEMORY_POINTER, NULL) : iodata->data.base;
    SDL_free(mem);
    SDL_free(userdata);
    return true;
}

static void dynamic_mem_setioprops(SDL_PropertiesID props, void *userdata)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) userdata;
    SDL_SetPointerProperty(props, SDL_PROP_IOSTREAM_DYNAMIC_MEMORY_POINTER, iodata->data.base);
    SDL_assert(iodata->props == 0);
    iodata->props = props;
}

SDL_IOStream *SDL_IOFromDynamicMem(void)
{
    IOStreamDynamicMemData *iodata = (IOStreamDynamicMemData *) SDL_calloc(1, sizeof (*iodata));
    if (!iodata) {
        return NULL;
    }

    SDL_IOStreamInterface iface;
    SDL_INIT_INTERFACE(&iface);
    iface.size = dynamic_mem_size;
    iface.seek = dynamic_mem_seek;
    iface.read = dynamic_mem_read;
    iface.write = dynamic_mem_write;
    iface.close = dynamic_mem_close;

    SDL_IOStream *iostr = SDL_OpenIO(&iface, iodata);
    if (!iostr) {
        SDL_free(iodata);
    } else {
        iostr->setioprops = dynamic_mem_setioprops;
    }

    return iostr;
}

SDL_IOStatus SDL_GetIOStatus(SDL_IOStream *context)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return SDL_IO_STATUS_ERROR;
    }
    return context->status;
}

SDL_IOStream *SDL_OpenIO(const SDL_IOStreamInterface *iface, void *userdata)
{
    CHECK_PARAM(!iface) {
        SDL_InvalidParamError("iface");
        return NULL;
    }
    CHECK_PARAM(iface->version < sizeof(*iface)) {
        // Update this to handle older versions of this interface
        SDL_SetError("Invalid interface, should be initialized with SDL_INIT_INTERFACE()");
        return NULL;
    }

    SDL_IOStream *iostr = (SDL_IOStream *)SDL_calloc(1, sizeof(*iostr));
    if (iostr) {
        SDL_copyp(&iostr->iface, iface);
        iostr->userdata = userdata;
    }
    return iostr;
}

bool SDL_CloseIO(SDL_IOStream *iostr)
{
    bool result = true;
    if (iostr) {
        if (iostr->iface.close) {
            result = iostr->iface.close(iostr->userdata);
        }
        SDL_DestroyProperties(iostr->props);
        SDL_free(iostr);
    }
    return result;
}

// Load all the data from an SDL data stream
void *SDL_LoadFile_IO(SDL_IOStream *src, size_t *datasize, bool closeio)
{
    const int FILE_CHUNK_SIZE = 1024;
    Sint64 size, size_total = 0;
    size_t size_read;
    char *data = NULL, *newdata;
    bool loading_chunks = false;

    CHECK_PARAM(!src) {
        SDL_InvalidParamError("src");
        goto done;
    }

    size = SDL_GetIOSize(src);
    if (size < 0) {
        size = FILE_CHUNK_SIZE;
        loading_chunks = true;
    }
    if (size >= SDL_SIZE_MAX - 1) {
        goto done;
    }
    data = (char *)SDL_malloc((size_t)(size + 1));
    if (!data) {
        goto done;
    }

    size_total = 0;
    for (;;) {
        if (loading_chunks) {
            if ((size_total + FILE_CHUNK_SIZE) > size) {
                size = (size_total + FILE_CHUNK_SIZE);
                if (size >= SDL_SIZE_MAX - 1) {
                    newdata = NULL;
                } else {
                    newdata = (char *)SDL_realloc(data, (size_t)(size + 1));
                }
                if (!newdata) {
                    SDL_free(data);
                    data = NULL;
                    goto done;
                }
                data = newdata;
            }
        }

        size_read = SDL_ReadIO(src, data + size_total, (size_t)(size - size_total));
        if (size_read > 0) {
            size_total += size_read;
            continue;
        } else if (SDL_GetIOStatus(src) == SDL_IO_STATUS_NOT_READY) {
            // Wait for the stream to be ready
            SDL_Delay(1);
            continue;
        }

        // The stream status will remain set for the caller to check
        break;
    }

    data[size_total] = '\0';

done:
    if (datasize) {
        *datasize = (size_t)size_total;
    }
    if (closeio && src) {
        SDL_CloseIO(src);
    }
    return data;
}

void *SDL_LoadFile(const char *file, size_t *datasize)
{
    SDL_IOStream *stream = SDL_IOFromFile(file, "rb");
    if (!stream) {
        if (datasize) {
            *datasize = 0;
        }
        return NULL;
    }
    return SDL_LoadFile_IO(stream, datasize, true);
}

bool SDL_SaveFile_IO(SDL_IOStream *src, const void *data, size_t datasize, bool closeio)
{
    size_t size_written = 0;
    size_t size_total = 0;
    bool success = true;

    CHECK_PARAM(!src) {
        SDL_InvalidParamError("src");
        goto done;
    }

    CHECK_PARAM(!data && datasize > 0) {
        SDL_InvalidParamError("data");
        goto done;
    }

    if (datasize > 0) {
        while (size_total < datasize) {
            size_written = SDL_WriteIO(src, ((const char *) data) + size_written, datasize - size_written);

            if (size_written <= 0) {
                if (SDL_GetIOStatus(src) == SDL_IO_STATUS_NOT_READY) {
                    // Wait for the stream to be ready
                    SDL_Delay(1);
                    continue;
                } else {
                    success = false;
                    goto done;
                }
            }

            size_total += size_written;
        }
    }

done:
    if (closeio && src) {
        SDL_CloseIO(src);
    }

    return success;
}

bool SDL_SaveFile(const char *file, const void *data, size_t datasize)
{
    SDL_IOStream *stream = SDL_IOFromFile(file, "wb");
    if (!stream) {
        return false;
    }
    return SDL_SaveFile_IO(stream, data, datasize, true);
}

SDL_PropertiesID SDL_GetIOProperties(SDL_IOStream *context)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return 0;
    }

    if (context->props == 0) {
        context->props = SDL_CreateProperties();
        if (context->props && context->setioprops) {
            context->setioprops(context->props, context->userdata);
            context->setioprops = NULL;  // NULL so we don't try to set props again, just in case.
        }
    }
    return context->props;
}

Sint64 SDL_GetIOSize(SDL_IOStream *context)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return -1;
    }

    if (!context->iface.size) {
        Sint64 pos, size;

        pos = SDL_SeekIO(context, 0, SDL_IO_SEEK_CUR);
        if (pos < 0) {
            return -1;
        }
        size = SDL_SeekIO(context, 0, SDL_IO_SEEK_END);

        SDL_SeekIO(context, pos, SDL_IO_SEEK_SET);
        return size;
    }
    return context->iface.size(context->userdata);
}

Sint64 SDL_SeekIO(SDL_IOStream *context, Sint64 offset, SDL_IOWhence whence)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return -1;
    }

    if (!context->iface.seek) {
        SDL_Unsupported();
        return -1;
    }
    return context->iface.seek(context->userdata, offset, whence);
}

Sint64 SDL_TellIO(SDL_IOStream *context)
{
    return SDL_SeekIO(context, 0, SDL_IO_SEEK_CUR);
}

size_t SDL_ReadIO(SDL_IOStream *context, void *ptr, size_t size)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return 0;
    }

    if (!context->iface.read) {
        context->status = SDL_IO_STATUS_WRITEONLY;
        SDL_Unsupported();
        return 0;
    }

    if (size == 0) {
        return 0;  // context->status doesn't change for this.
    }

    context->status = SDL_IO_STATUS_READY;
    SDL_ClearError();

    return context->iface.read(context->userdata, ptr, size, &context->status);
}

size_t SDL_WriteIO(SDL_IOStream *context, const void *ptr, size_t size)
{
    CHECK_PARAM(!context) {
        SDL_InvalidParamError("context");
        return 0;
    }

    if (!context->iface.write) {
        context->status = SDL_IO_STATUS_READONLY;
        SDL_Unsupported();
        return 0;
    }

    if (size == 0) {
        return 0;  // context->status doesn't change for this.
    }

    context->status = SDL_IO_STATUS_READY;
    SDL_ClearError();

    return context->iface.write(context->userdata, ptr, size, &context->status);
}

size_t SDL_IOprintf(SDL_IOStream *context, SDL_PRINTF_FORMAT_STRING const char *fmt, ...)
{
    va_list ap;
    int size;
    char *string;
    size_t bytes;

    va_start(ap, fmt);
    size = SDL_vasprintf(&string, fmt, ap);
    va_end(ap);
    if (size < 0) {
        return 0;
    }

    bytes = SDL_WriteIO(context, string, (size_t)size);
    SDL_free(string);
    return bytes;
}

size_t SDL_IOvprintf(SDL_IOStream *context, SDL_PRINTF_FORMAT_STRING const char *fmt, va_list ap)
{
    int size;
    char *string;
    size_t bytes;

    size = SDL_vasprintf(&string, fmt, ap);
    if (size < 0) {
        return 0;
    }

    bytes = SDL_WriteIO(context, string, (size_t)size);
    SDL_free(string);
    return bytes;
}

bool SDL_FlushIO(SDL_IOStream *context)
{
    bool result = true;

    CHECK_PARAM(!context) {
        return SDL_InvalidParamError("context");
    }

    context->status = SDL_IO_STATUS_READY;
    SDL_ClearError();

    if (context->iface.flush) {
        result = context->iface.flush(context->userdata, &context->status);
    }
    if (!result && (context->status == SDL_IO_STATUS_READY)) {
        context->status = SDL_IO_STATUS_ERROR;
    }
    return result;
}

// Functions for dynamically reading and writing endian-specific values

bool SDL_ReadU8(SDL_IOStream *src, Uint8 *value)
{
    Uint8 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = data;
    }
    return result;
}

bool SDL_ReadS8(SDL_IOStream *src, Sint8 *value)
{
    Sint8 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = data;
    }
    return result;
}

bool SDL_ReadU16LE(SDL_IOStream *src, Uint16 *value)
{
    Uint16 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap16LE(data);
    }
    return result;
}

bool SDL_ReadS16LE(SDL_IOStream *src, Sint16 *value)
{
    return SDL_ReadU16LE(src, (Uint16 *)value);
}

bool SDL_ReadU16BE(SDL_IOStream *src, Uint16 *value)
{
    Uint16 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap16BE(data);
    }
    return result;
}

bool SDL_ReadS16BE(SDL_IOStream *src, Sint16 *value)
{
    return SDL_ReadU16BE(src, (Uint16 *)value);
}

bool SDL_ReadU32LE(SDL_IOStream *src, Uint32 *value)
{
    Uint32 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap32LE(data);
    }
    return result;
}

bool SDL_ReadS32LE(SDL_IOStream *src, Sint32 *value)
{
    return SDL_ReadU32LE(src, (Uint32 *)value);
}

bool SDL_ReadU32BE(SDL_IOStream *src, Uint32 *value)
{
    Uint32 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap32BE(data);
    }
    return result;
}

bool SDL_ReadS32BE(SDL_IOStream *src, Sint32 *value)
{
    return SDL_ReadU32BE(src, (Uint32 *)value);
}

bool SDL_ReadU64LE(SDL_IOStream *src, Uint64 *value)
{
    Uint64 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap64LE(data);
    }
    return result;
}

bool SDL_ReadS64LE(SDL_IOStream *src, Sint64 *value)
{
    return SDL_ReadU64LE(src, (Uint64 *)value);
}

bool SDL_ReadU64BE(SDL_IOStream *src, Uint64 *value)
{
    Uint64 data = 0;
    bool result = false;

    if (SDL_ReadIO(src, &data, sizeof(data)) == sizeof(data)) {
        result = true;
    }
    if (value) {
        *value = SDL_Swap64BE(data);
    }
    return result;
}

bool SDL_ReadS64BE(SDL_IOStream *src, Sint64 *value)
{
    return SDL_ReadU64BE(src, (Uint64 *)value);
}

bool SDL_WriteU8(SDL_IOStream *dst, Uint8 value)
{
    return (SDL_WriteIO(dst, &value, sizeof(value)) == sizeof(value));
}

bool SDL_WriteS8(SDL_IOStream *dst, Sint8 value)
{
    return (SDL_WriteIO(dst, &value, sizeof(value)) == sizeof(value));
}

bool SDL_WriteU16LE(SDL_IOStream *dst, Uint16 value)
{
    const Uint16 swapped = SDL_Swap16LE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS16LE(SDL_IOStream *dst, Sint16 value)
{
    return SDL_WriteU16LE(dst, (Uint16)value);
}

bool SDL_WriteU16BE(SDL_IOStream *dst, Uint16 value)
{
    const Uint16 swapped = SDL_Swap16BE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS16BE(SDL_IOStream *dst, Sint16 value)
{
    return SDL_WriteU16BE(dst, (Uint16)value);
}

bool SDL_WriteU32LE(SDL_IOStream *dst, Uint32 value)
{
    const Uint32 swapped = SDL_Swap32LE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS32LE(SDL_IOStream *dst, Sint32 value)
{
    return SDL_WriteU32LE(dst, (Uint32)value);
}

bool SDL_WriteU32BE(SDL_IOStream *dst, Uint32 value)
{
    const Uint32 swapped = SDL_Swap32BE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS32BE(SDL_IOStream *dst, Sint32 value)
{
    return SDL_WriteU32BE(dst, (Uint32)value);
}

bool SDL_WriteU64LE(SDL_IOStream *dst, Uint64 value)
{
    const Uint64 swapped = SDL_Swap64LE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS64LE(SDL_IOStream *dst, Sint64 value)
{
    return SDL_WriteU64LE(dst, (Uint64)value);
}

bool SDL_WriteU64BE(SDL_IOStream *dst, Uint64 value)
{
    const Uint64 swapped = SDL_Swap64BE(value);
    return (SDL_WriteIO(dst, &swapped, sizeof(swapped)) == sizeof(swapped));
}

bool SDL_WriteS64BE(SDL_IOStream *dst, Sint64 value)
{
    return SDL_WriteU64BE(dst, (Uint64)value);
}
