src/file/SDL_rwops.c

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/
#include "SDL_config.h"

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

#include "SDL_endian.h"
#include "SDL_rwops.h"


#ifdef __WIN32__

/* Functions to read/write Win32 API file pointers */
/* Will not use it on WinCE because stdio is buffered, it means
   faster, and all stdio functions anyway are embedded in coredll.dll - 
   the main wince dll*/

#define WINDOWS_LEAN_AND_MEAN
#include <windows.h>

#ifndef INVALID_SET_FILE_POINTER
#define INVALID_SET_FILE_POINTER 0xFFFFFFFF
#endif

#define READAHEAD_BUFFER_SIZE	1024

static int SDLCALL
win32_file_open(SDL_RWops * context, const char *filename, const char *mode)
{
#ifndef _WIN32_WCE
    UINT old_error_mode;
#endif
    HANDLE h;
    DWORD r_right, w_right;
    DWORD must_exist, truncate;
    int a_mode;

    if (!context)
        return -1;

    context->hidden.win32io.h = INVALID_HANDLE_VALUE;   /* mark this as unusable */

    context->hidden.win32io.buffer.data =
        (char *) SDL_malloc(READAHEAD_BUFFER_SIZE);
    if (!context->hidden.win32io.buffer.data) {
        SDL_OutOfMemory();
        return -1;
    }
    context->hidden.win32io.buffer.size = 0;
    context->hidden.win32io.buffer.left = 0;

    /* "r" = reading, file must exist */
    /* "w" = writing, truncate existing, file may 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    */

    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 (!r_right && !w_right)   /* inconsistent mode */
        return -1;              /* failed (invalid call) */

#ifdef _WIN32_WCE
    {
        size_t size = SDL_strlen(filename) + 1;
        wchar_t *filenameW = SDL_stack_alloc(wchar_t, size);

        if (MultiByteToWideChar(CP_UTF8, 0, filename, -1, filenameW, size) ==
            0) {
            SDL_SetError("Unable to convert filename to Unicode");
            SDL_stack_free(filenameW);
            return -1;
        }
        h = CreateFile(filenameW, (w_right | r_right),
                       (w_right) ? 0 : FILE_SHARE_READ, NULL,
                       (must_exist | truncate | a_mode),
                       FILE_ATTRIBUTE_NORMAL, NULL);
        SDL_stack_free(filenameW);
    }
#else
    /* Do not open a dialog box if failure */
    old_error_mode =
        SetErrorMode(SEM_NOOPENFILEERRORBOX | SEM_FAILCRITICALERRORS);

    h = CreateFile(filename, (w_right | r_right),
                   (w_right) ? 0 : FILE_SHARE_READ, NULL,
                   (must_exist | truncate | a_mode), FILE_ATTRIBUTE_NORMAL,
                   NULL);

    /* restore old behaviour */
    SetErrorMode(old_error_mode);
#endif /* _WIN32_WCE */

    if (h == INVALID_HANDLE_VALUE) {
        SDL_SetError("Couldn't open %s", filename);
        return -2;              /* failed (CreateFile) */
    }
    context->hidden.win32io.h = h;
    context->hidden.win32io.append = a_mode ? SDL_TRUE : SDL_FALSE;

    return 0;                   /* ok */
}
static long SDLCALL
win32_file_seek(SDL_RWops * context, long offset, int whence)
{
    DWORD win32whence;
    long file_pos;

    if (!context || context->hidden.win32io.h == INVALID_HANDLE_VALUE) {
        SDL_SetError("win32_file_seek: invalid context/file not opened");
        return -1;
    }

    /* FIXME: We may be able to satisfy the seek within buffered data */
    if (whence == RW_SEEK_CUR && context->hidden.win32io.buffer.left) {
        offset -= context->hidden.win32io.buffer.left;
    }
    context->hidden.win32io.buffer.left = 0;

    switch (whence) {
    case RW_SEEK_SET:
        win32whence = FILE_BEGIN;
        break;
    case RW_SEEK_CUR:
        win32whence = FILE_CURRENT;
        break;
    case RW_SEEK_END:
        win32whence = FILE_END;
        break;
    default:
        SDL_SetError("win32_file_seek: Unknown value for 'whence'");
        return -1;
    }

    file_pos =
        SetFilePointer(context->hidden.win32io.h, offset, NULL, win32whence);

    if (file_pos != INVALID_SET_FILE_POINTER)
        return file_pos;        /* success */

    SDL_Error(SDL_EFSEEK);
    return -1;                  /* error */
}
static size_t SDLCALL
win32_file_read(SDL_RWops * context, void *ptr, size_t size, size_t maxnum)
{
    size_t total_need;
    size_t total_read = 0;
    size_t read_ahead;
    DWORD byte_read;

    total_need = size * maxnum;

    if (!context || context->hidden.win32io.h == INVALID_HANDLE_VALUE
        || !total_need)
        return 0;

    if (context->hidden.win32io.buffer.left > 0) {
        void *data = (char *) context->hidden.win32io.buffer.data +
            context->hidden.win32io.buffer.size -
            context->hidden.win32io.buffer.left;
        read_ahead = SDL_min(total_need, context->hidden.win32io.buffer.left);
        SDL_memcpy(ptr, data, read_ahead);
        context->hidden.win32io.buffer.left -= read_ahead;

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

    if (total_need < READAHEAD_BUFFER_SIZE) {
        if (!ReadFile
            (context->hidden.win32io.h, context->hidden.win32io.buffer.data,
             READAHEAD_BUFFER_SIZE, &byte_read, NULL)) {
            SDL_Error(SDL_EFREAD);
            return 0;
        }
        read_ahead = SDL_min(total_need, (int) byte_read);
        SDL_memcpy(ptr, context->hidden.win32io.buffer.data, read_ahead);
        context->hidden.win32io.buffer.size = byte_read;
        context->hidden.win32io.buffer.left = byte_read - read_ahead;
        total_read += read_ahead;
    } else {
        if (!ReadFile
            (context->hidden.win32io.h, ptr, total_need, &byte_read, NULL)) {
            SDL_Error(SDL_EFREAD);
            return 0;
        }
        total_read += byte_read;
    }
    return (total_read / size);
}
static size_t SDLCALL
win32_file_write(SDL_RWops * context, const void *ptr, size_t size,
                 size_t num)
{

    size_t total_bytes;
    DWORD byte_written, nwritten;

    total_bytes = size * num;

    if (!context || context->hidden.win32io.h == INVALID_HANDLE_VALUE
        || total_bytes <= 0 || !size)
        return 0;

    if (context->hidden.win32io.buffer.left) {
        SetFilePointer(context->hidden.win32io.h,
                       -context->hidden.win32io.buffer.left, NULL,
                       FILE_CURRENT);
        context->hidden.win32io.buffer.left = 0;
    }

    /* if in append mode, we must go to the EOF before write */
    if (context->hidden.win32io.append) {
        if (SetFilePointer(context->hidden.win32io.h, 0L, NULL, FILE_END) ==
            INVALID_SET_FILE_POINTER) {
            SDL_Error(SDL_EFWRITE);
            return 0;
        }
    }

    if (!WriteFile
        (context->hidden.win32io.h, ptr, total_bytes, &byte_written, NULL)) {
        SDL_Error(SDL_EFWRITE);
        return 0;
    }

    nwritten = byte_written / size;
    return nwritten;
}
static int SDLCALL
win32_file_close(SDL_RWops * context)
{

    if (context) {
        if (context->hidden.win32io.h != INVALID_HANDLE_VALUE) {
            CloseHandle(context->hidden.win32io.h);
            context->hidden.win32io.h = INVALID_HANDLE_VALUE;   /* to be sure */
        }
        if (context->hidden.win32io.buffer.data) {
            SDL_free(context->hidden.win32io.buffer.data);
            context->hidden.win32io.buffer.data = NULL;
        }
        SDL_FreeRW(context);
    }
    return (0);
}
#endif /* __WIN32__ */

#ifdef HAVE_STDIO_H

/* Functions to read/write stdio file pointers */

static long SDLCALL
stdio_seek(SDL_RWops * context, long offset, int whence)
{
    if (fseek(context->hidden.stdio.fp, offset, whence) == 0) {
        return (ftell(context->hidden.stdio.fp));
    } else {
        SDL_Error(SDL_EFSEEK);
        return (-1);
    }
}
static size_t SDLCALL
stdio_read(SDL_RWops * context, void *ptr, size_t size, size_t maxnum)
{
    size_t nread;

    nread = fread(ptr, size, maxnum, context->hidden.stdio.fp);
    if (nread == 0 && ferror(context->hidden.stdio.fp)) {
        SDL_Error(SDL_EFREAD);
    }
    return (nread);
}
static size_t SDLCALL
stdio_write(SDL_RWops * context, const void *ptr, size_t size, size_t num)
{
    size_t nwrote;

    nwrote = fwrite(ptr, size, num, context->hidden.stdio.fp);
    if (nwrote == 0 && ferror(context->hidden.stdio.fp)) {
        SDL_Error(SDL_EFWRITE);
    }
    return (nwrote);
}
static int SDLCALL
stdio_close(SDL_RWops * context)
{
    int status = 0;
    if (context) {
        if (context->hidden.stdio.autoclose) {
            /* WARNING:  Check the return value here! */
            if (fclose(context->hidden.stdio.fp) != 0) {
                SDL_Error(SDL_EFWRITE);
                status = -1;
            }
        }
        SDL_FreeRW(context);
    }
    return status;
}
#endif /* !HAVE_STDIO_H */

/* Functions to read/write memory pointers */

static long SDLCALL
mem_seek(SDL_RWops * context, long offset, int whence)
{
    Uint8 *newpos;

    switch (whence) {
    case RW_SEEK_SET:
        newpos = context->hidden.mem.base + offset;
        break;
    case RW_SEEK_CUR:
        newpos = context->hidden.mem.here + offset;
        break;
    case RW_SEEK_END:
        newpos = context->hidden.mem.stop + offset;
        break;
    default:
        SDL_SetError("Unknown value for 'whence'");
        return (-1);
    }
    if (newpos < context->hidden.mem.base) {
        newpos = context->hidden.mem.base;
    }
    if (newpos > context->hidden.mem.stop) {
        newpos = context->hidden.mem.stop;
    }
    context->hidden.mem.here = newpos;
    return (context->hidden.mem.here - context->hidden.mem.base);
}
static size_t SDLCALL
mem_read(SDL_RWops * context, void *ptr, size_t size, size_t maxnum)
{
    size_t total_bytes;
    size_t mem_available;

    total_bytes = (maxnum * size);
    if ((maxnum <= 0) || (size <= 0)
        || ((total_bytes / maxnum) != (size_t) size)) {
        return 0;
    }

    mem_available = (context->hidden.mem.stop - context->hidden.mem.here);
    if (total_bytes > mem_available) {
        total_bytes = mem_available;
    }

    SDL_memcpy(ptr, context->hidden.mem.here, total_bytes);
    context->hidden.mem.here += total_bytes;

    return (total_bytes / size);
}
static size_t SDLCALL
mem_write(SDL_RWops * context, const void *ptr, size_t size, size_t num)
{
    if ((context->hidden.mem.here + (num * size)) > context->hidden.mem.stop) {
        num = (context->hidden.mem.stop - context->hidden.mem.here) / size;
    }
    SDL_memcpy(context->hidden.mem.here, ptr, num * size);
    context->hidden.mem.here += num * size;
    return (num);
}
static size_t SDLCALL
mem_writeconst(SDL_RWops * context, const void *ptr, size_t size, size_t num)
{
    SDL_SetError("Can't write to read-only memory");
    return (-1);
}
static int SDLCALL
mem_close(SDL_RWops * context)
{
    if (context) {
        SDL_FreeRW(context);
    }
    return (0);
}


/* Functions to create SDL_RWops structures from various data sources */

SDL_RWops *
SDL_RWFromFile(const char *file, const char *mode)
{
    SDL_RWops *rwops = NULL;
#ifdef HAVE_STDIO_H
    FILE *fp = NULL;
#endif
    if (!file || !*file || !mode || !*mode) {
        SDL_SetError("SDL_RWFromFile(): No file or no mode specified");
        return NULL;
    }
#if defined(__WIN32__)
    rwops = SDL_AllocRW();
    if (!rwops)
        return NULL;            /* SDL_SetError already setup by SDL_AllocRW() */
    rwops->hidden.win32io.h = INVALID_HANDLE_VALUE;
    if (win32_file_open(rwops, file, mode)) {
        SDL_FreeRW(rwops);
        return NULL;
    }
    rwops->seek = win32_file_seek;
    rwops->read = win32_file_read;
    rwops->write = win32_file_write;
    rwops->close = win32_file_close;

#elif HAVE_STDIO_H

    fp = fopen(file, mode);
    if (fp == NULL) {
        SDL_SetError("Couldn't open %s", file);
    } else {
        rwops = SDL_RWFromFP(fp, 1);
    }
#else
    SDL_SetError("SDL not compiled with stdio support");
#endif /* !HAVE_STDIO_H */

    return (rwops);
}

#ifdef HAVE_STDIO_H
SDL_RWops *
SDL_RWFromFP(FILE * fp, SDL_bool autoclose)
{
    SDL_RWops *rwops = NULL;

    rwops = SDL_AllocRW();
    if (rwops != NULL) {
        rwops->seek = stdio_seek;
        rwops->read = stdio_read;
        rwops->write = stdio_write;
        rwops->close = stdio_close;
        rwops->hidden.stdio.fp = fp;
        rwops->hidden.stdio.autoclose = autoclose;
    }
    return (rwops);
}
#endif /* HAVE_STDIO_H */

SDL_RWops *
SDL_RWFromMem(void *mem, int size)
{
    SDL_RWops *rwops;

    rwops = SDL_AllocRW();
    if (rwops != NULL) {
        rwops->seek = mem_seek;
        rwops->read = mem_read;
        rwops->write = mem_write;
        rwops->close = mem_close;
        rwops->hidden.mem.base = (Uint8 *) mem;
        rwops->hidden.mem.here = rwops->hidden.mem.base;
        rwops->hidden.mem.stop = rwops->hidden.mem.base + size;
    }
    return (rwops);
}

SDL_RWops *
SDL_RWFromConstMem(const void *mem, int size)
{
    SDL_RWops *rwops;

    rwops = SDL_AllocRW();
    if (rwops != NULL) {
        rwops->seek = mem_seek;
        rwops->read = mem_read;
        rwops->write = mem_writeconst;
        rwops->close = mem_close;
        rwops->hidden.mem.base = (Uint8 *) mem;
        rwops->hidden.mem.here = rwops->hidden.mem.base;
        rwops->hidden.mem.stop = rwops->hidden.mem.base + size;
    }
    return (rwops);
}

SDL_RWops *
SDL_AllocRW(void)
{
    SDL_RWops *area;

    area = (SDL_RWops *) SDL_malloc(sizeof *area);
    if (area == NULL) {
        SDL_OutOfMemory();
    }
    return (area);
}

void
SDL_FreeRW(SDL_RWops * area)
{
    SDL_free(area);
}

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

Uint16
SDL_ReadLE16(SDL_RWops * src)
{
    Uint16 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapLE16(value));
}

Uint16
SDL_ReadBE16(SDL_RWops * src)
{
    Uint16 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapBE16(value));
}

Uint32
SDL_ReadLE32(SDL_RWops * src)
{
    Uint32 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapLE32(value));
}

Uint32
SDL_ReadBE32(SDL_RWops * src)
{
    Uint32 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapBE32(value));
}

Uint64
SDL_ReadLE64(SDL_RWops * src)
{
    Uint64 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapLE64(value));
}

Uint64
SDL_ReadBE64(SDL_RWops * src)
{
    Uint64 value;

    SDL_RWread(src, &value, (sizeof value), 1);
    return (SDL_SwapBE64(value));
}

int
SDL_WriteLE16(SDL_RWops * dst, Uint16 value)
{
    value = SDL_SwapLE16(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

int
SDL_WriteBE16(SDL_RWops * dst, Uint16 value)
{
    value = SDL_SwapBE16(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

int
SDL_WriteLE32(SDL_RWops * dst, Uint32 value)
{
    value = SDL_SwapLE32(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

int
SDL_WriteBE32(SDL_RWops * dst, Uint32 value)
{
    value = SDL_SwapBE32(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

int
SDL_WriteLE64(SDL_RWops * dst, Uint64 value)
{
    value = SDL_SwapLE64(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

int
SDL_WriteBE64(SDL_RWops * dst, Uint64 value)
{
    value = SDL_SwapBE64(value);
    return (SDL_RWwrite(dst, &value, (sizeof value), 1));
}

/* vi: set ts=4 sw=4 expandtab: */