ioapi_mem.c

/* ioapi_mem.h -- IO base function header for compress/uncompress .zip
   files using zlib + zip or unzip API

   This version of ioapi is designed to access memory rather than files.
   We do use a region of memory to put data in to and take it out of. We do
   not have auto-extending buffers and do not inform anyone else that the
   data has been written. It is really intended for accessing a zip archive
   embedded in an application such that I can write an installer with no
   external files. Creation of archives has not been attempted, although
   parts of the framework are present.

   Based on Unzip ioapi.c version 0.22, May 19th, 2003

   Copyright (C) 1998-2003 Gilles Vollant
             (C) 2003 Justin Fletcher

   This file is under the same license as the Unzip tool it is distributed
   with.
*/


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "zlib.h"
#include "ioapi.h"

#include "ioapi_mem.h"

#ifndef IOMEM_BUFFERSIZE
#  define IOMEM_BUFFERSIZE (64 * 1024)
#endif 

voidpf ZCALLBACK fopen_mem_func (opaque, filename, mode)
   voidpf opaque;
   const char* filename;
   int mode;
{
    ourmemory_t *mem = (ourmemory_t *)opaque;
    if (mem == NULL)
        return NULL; /* Mem structure passed in was null */
    
    if (mode & ZLIB_FILEFUNC_MODE_CREATE)
    {
        if (mem->grow)
        {
            mem->size = IOMEM_BUFFERSIZE;
            mem->base = (char *)malloc(mem->size);
        }

        mem->limit = 0; /* When writing we start with 0 bytes written */
    }
    else
        mem->limit = mem->size;

    mem->cur_offset = 0;

    return mem;
}

voidpf ZCALLBACK fopendisk_mem_func (opaque, stream, number_disk, mode)
   voidpf opaque;
   voidpf stream;
   int number_disk;
   int mode;
{
    /* Not used */
    return NULL;
}

uLong ZCALLBACK fread_mem_func (opaque, stream, buf, size)
   voidpf opaque;
   voidpf stream;
   void* buf;
   uLong size;
{
    ourmemory_t *mem = (ourmemory_t *)stream;

    if (size > mem->size - mem->cur_offset)
        size = mem->size - mem->cur_offset;

    memcpy(buf, mem->base + mem->cur_offset, size);
    mem->cur_offset += size;

    return size;
}


uLong ZCALLBACK fwrite_mem_func (opaque, stream, buf, size)
   voidpf opaque;
   voidpf stream;
   const void* buf;
   uLong size;
{
    ourmemory_t *mem = (ourmemory_t *)stream;
    char *newbase = NULL;
    uLong newmemsize = 0;

    if (size > mem->size - mem->cur_offset)
    {
        if (mem->grow)
        {
            newmemsize = mem->size;
            if (size < IOMEM_BUFFERSIZE)
                newmemsize += IOMEM_BUFFERSIZE;
            else
                newmemsize += size;
            newbase = (char *)malloc(newmemsize);
            memcpy(newbase, mem->base, mem->size);
            free(mem->base);
            mem->base = newbase;
            mem->size = newmemsize;
        }
        else
            size = mem->size - mem->cur_offset;
    }
    memcpy(mem->base + mem->cur_offset, buf, size);
    mem->cur_offset += size;
    if (mem->cur_offset > mem->limit)
        mem->limit = mem->cur_offset;

    return size;
}

long ZCALLBACK ftell_mem_func (opaque, stream)
   voidpf opaque;
   voidpf stream;
{
    ourmemory_t *mem = (ourmemory_t *)stream;
    return mem->cur_offset;
}

long ZCALLBACK fseek_mem_func (opaque, stream, offset, origin)
   voidpf opaque;
   voidpf stream;
   uLong offset;
   int origin;
{
    ourmemory_t *mem = (ourmemory_t *)stream;
    uLong new_pos;
    switch (origin)
    {
        case ZLIB_FILEFUNC_SEEK_CUR:
            new_pos = mem->cur_offset + offset;
            break;
        case ZLIB_FILEFUNC_SEEK_END:
            new_pos = mem->limit + offset;
            break;
        case ZLIB_FILEFUNC_SEEK_SET:
            new_pos = offset;
            break;
        default: 
            return -1;
    }

    if (new_pos > mem->size)
        return 1; /* Failed to seek that far */
    mem->cur_offset = new_pos;
    return 0;
}

int ZCALLBACK fclose_mem_func (opaque, stream)
   voidpf opaque;
   voidpf stream;
{
    /* Even with grow = 1, caller must always free() memory */
    return 0;
}

int ZCALLBACK ferror_mem_func (opaque, stream)
   voidpf opaque;
   voidpf stream;
{
    /* We never return errors */
    return 0;
}

void fill_memory_filefunc (pzlib_filefunc_def, ourmem)
   zlib_filefunc_def* pzlib_filefunc_def;
   ourmemory_t *ourmem;
{
    pzlib_filefunc_def->zopen_file = fopen_mem_func;
    pzlib_filefunc_def->zopendisk_file = fopendisk_mem_func;
    pzlib_filefunc_def->zread_file = fread_mem_func;
    pzlib_filefunc_def->zwrite_file = fwrite_mem_func;
    pzlib_filefunc_def->ztell_file = ftell_mem_func;
    pzlib_filefunc_def->zseek_file = fseek_mem_func;
    pzlib_filefunc_def->zclose_file = fclose_mem_func;
    pzlib_filefunc_def->zerror_file = ferror_mem_func;
    pzlib_filefunc_def->opaque = ourmem;
}