176 lines
5.0 KiB
C
176 lines
5.0 KiB
C
/* libgbfs.c
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access object in a GBFS file
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Copyright 2002-2004 Damian Yerrick
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
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OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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IN THE SOFTWARE.
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*/
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/* This code assumes a LITTLE ENDIAN target. It'll need a boatload
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of itohs and itohl calls if converted to run on Sega Genesis. It
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also assumes that the target uses 16-bit short and 32-bit longs.
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*/
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typedef unsigned short u16;
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typedef unsigned long u32;
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#include <stdlib.h>
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#include <string.h>
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#include "gbfs.h"
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/* change this to the end of your ROM, or to 0x02040000 for multiboot */
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#define GBFS_1ST_SEARCH_LIMIT ((const u32 *)0x02040000)
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#define GBFS_2ND_SEARCH_START ((const u32 *)0x08000000)
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#define GBFS_2ND_SEARCH_LIMIT ((const u32 *)0x0a000000)
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/* a power of two, less than or equal to the argument passed to
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padbin. Increasing the stride makes find_first_gbfs_file()
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faster at the cost of a slightly larger binary. */
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#define GBFS_ALIGNMENT 256
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const GBFS_FILE *find_first_gbfs_file(const void *start)
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{
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/* align the pointer */
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const u32 *here = (const u32 *)
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((unsigned long)start & (-GBFS_ALIGNMENT));
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const char rest_of_magic[] = "ightGBFS\r\n\x1a\n";
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/* Linear-search first in multiboot space. */
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while(here < GBFS_1ST_SEARCH_LIMIT)
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{
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/* We have to keep the magic code in two pieces; otherwise,
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this function may find itself and think it's a GBFS file.
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This obviously won't work if your compiler stores this
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numeric literal just before the literal string, but Devkit
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Advance R4 and R5 seem to keep numeric constant pools
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separate enough from string pools for this to work.
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*/
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if(*here == 0x456e6950) /* ASCII code for little endian "PinE" */
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{
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/* We've matched the first four bytes.
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If the rest of the magic matches, then we've found a file. */
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if(!memcmp(here + 1, rest_of_magic, 12))
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return (const GBFS_FILE *)here;
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}
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here += GBFS_ALIGNMENT / sizeof(*here);
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}
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/* Now search in ROM space. */
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if(here < GBFS_2ND_SEARCH_START)
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here = GBFS_2ND_SEARCH_START;
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while(here < GBFS_2ND_SEARCH_LIMIT)
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{
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/* Search loop same as above. */
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if(*here == 0x456e6950) /* ASCII code for little endian "PinE" */
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{
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if(!memcmp(here + 1, rest_of_magic, 12))
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return (const GBFS_FILE *)here;
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}
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here += GBFS_ALIGNMENT / sizeof(*here);
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}
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return 0;
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}
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const void *skip_gbfs_file(const GBFS_FILE *file)
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{
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return ((char *)file + file->total_len);
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}
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static int namecmp(const void *a, const void *b)
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{
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return memcmp(a, b, 24);
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}
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const void *gbfs_get_obj(const GBFS_FILE *file,
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const char *name,
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u32 *len)
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{
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char key[24] = {0};
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const GBFS_ENTRY *dirbase = (const GBFS_ENTRY *)((const char *)file + file->dir_off);
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size_t n_entries = file->dir_nmemb;
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const GBFS_ENTRY *here;
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strncpy(key, name, 23);
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here = bsearch(key, dirbase,
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n_entries, sizeof(GBFS_ENTRY),
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namecmp);
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if(!here)
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return NULL;
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if(len)
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*len = here->len;
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return (char *)file + here->data_offset;
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}
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const void *gbfs_get_nth_obj(const GBFS_FILE *file,
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size_t n,
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char *name,
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u32 *len)
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{
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const GBFS_ENTRY *dirbase = (const GBFS_ENTRY *)((const char *)file + file->dir_off);
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size_t n_entries = file->dir_nmemb;
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const GBFS_ENTRY *here = dirbase + n;
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if(n >= n_entries)
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return NULL;
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if(name)
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{
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strncpy(name, here->name, 24);
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name[24] = 0;
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}
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if(len)
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*len = here->len;
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return (char *)file + here->data_offset;
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}
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void *gbfs_copy_obj(void *dst,
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const GBFS_FILE *file,
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const char *name)
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{
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u32 len;
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const void *src = gbfs_get_obj(file, name, &len);
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if(!src)
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return NULL;
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memcpy(dst, src, len);
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return dst;
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}
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size_t gbfs_count_objs(const GBFS_FILE *file)
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{
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return file ? file->dir_nmemb : 0;
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}
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