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* Copyright (c) 2001, 2002 Michael J. Roberts. All Rights Reserved.
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* Please see the accompanying license file, LICENSE.TXT, for information
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* on using and copying this software.
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resfind.cpp - find a multimedia resource in a tads 2 or tads 3 game file
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Searches a compiled tads 2 game file or a compiled tads 3 image file
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for a multimedia resource of a given name. The caller doesn't have to
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know which tads version created the file; we'll sense the file type and
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This implementation is independent of any tads 2 or tads 3 subsystem
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except osifc, which it uses for portable file I/O and portable byte
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09/24/01 MJRoberts - Creation
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/* ------------------------------------------------------------------------ */
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* tads 2 file signature
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#define T2_SIG "TADS2 bin\012\015\032"
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* tads 3 file signature
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#define T3_SIG "T3-image\015\012\032"
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/* ------------------------------------------------------------------------ */
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* Find a resource in a tads 2 game file
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static int t2_find_res(osfildef *fp, const char *resname,
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unsigned long startpos;
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/* we haven't found what we're looking for yet */
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/* note the length of the name we're seeking */
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resname_len = strlen(resname);
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* note the seek location of the start of the tads 2 game file stream
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* within the file - if the game file is embedded in a larger file
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* stream, the seek locations we find within the file are relative to
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* this starting location
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startpos = osfpos(fp);
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* skip past the tads 2 file header (13 bytes for the signature, 7
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* bytes for the version header, 2 bytes for the flags, 26 bytes for
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osfseek(fp, 13 + 7 + 2 + 26, OSFSK_CUR);
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* scan the sections in the file; stop on $EOF, and skip everything
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* else but HTMLRES, which is the section type that
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/* read the section type and next-section pointer */
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|| osfrb(fp, buf + 1, (int)((unsigned char)buf[0] + 4)))
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/* failed to read it - give up */
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/* note the ending position of this section */
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endofs = t3rp4u(buf + 1 + (unsigned char)buf[0]);
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if (buf[0] == 7 && memcmp(buf+1, "HTMLRES", 7) == 0)
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unsigned long entry_cnt;
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* It's a multimedia resource block. Read the index table
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* header (which contains the number of entries and a reserved
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if (osfrb(fp, buf, 8))
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/* get the number of entries from the header */
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entry_cnt = t3rp4u(buf);
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/* read the entries */
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for (i = 0 ; i < entry_cnt ; ++i)
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unsigned long res_ofs;
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unsigned long res_siz;
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unsigned short name_len;
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/* read the entry header */
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if (osfrb(fp, buf, 10))
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/* parse the header */
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res_ofs = t3rp4u(buf);
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res_siz = t3rp4u(buf + 4);
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name_len = osrp2(buf + 8);
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/* read the entry's name */
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if (name_len > sizeof(buf) || osfrb(fp, buf, name_len))
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* if it matches the name we're looking for, note that we
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if (name_len == resname_len
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&& memicmp(resname, buf, name_len) == 0)
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* note that we found it, and note its resource size
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* and offset in the return structure - but keep
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* scanning the rest of the directory, since we need
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* to know where the directory ends to know where the
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* actual resources begin
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info->seek_pos = res_ofs;
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* if we found our resource, the current seek position is the
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* base of the offset we found in the directory; so fix up the
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* offset to give the actual file location
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/* fix up the offset with the actual file location */
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info->seek_pos += osfpos(fp);
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/* tell the caller we found it */
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/* we didn't find it - seek to the end of this section */
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osfseek(fp, endofs + startpos, OSFSK_SET);
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else if (buf[0] == 4 && memcmp(buf+1, "$EOF", 4) == 0)
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* that's the end of the file - we've finished without finding
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* the resource, so return failure
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* this isn't a section we're interested in - skip to the end
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* of the section and keep going
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osfseek(fp, endofs + startpos, OSFSK_SET);
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/* ------------------------------------------------------------------------ */
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* Find a resource in a T3 image file
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static int t3_find_res(osfildef *fp, const char *resname,
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/* note the length of the name we're seeking */
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resname_len = strlen(resname);
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* skip the file header - 11 bytes for the signature, 2 bytes for the
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* format version, 32 reserved bytes, and 24 bytes for the timestamp
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osfseek(fp, 11 + 2 + 32 + 24, OSFSK_CUR);
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/* scan the data blocks */
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/* read the block header */
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if (osfrb(fp, buf, 10))
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/* get the block size */
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siz = t3rp4u(buf + 4);
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if (memcmp(buf, "MRES", 4) == 0)
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unsigned long base_ofs;
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unsigned int entry_cnt;
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* remember the current seek position - the data seek location
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* for each index entry is given as an offset from this
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base_ofs = osfpos(fp);
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/* read the number of entries */
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if (osfrb(fp, buf, 2))
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/* parse the entry count */
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entry_cnt = osrp2(buf);
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/* read the entries */
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for (i = 0 ; i < entry_cnt ; ++i)
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unsigned long entry_ofs;
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unsigned long entry_siz;
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unsigned int entry_name_len;
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/* read this index entry's header */
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if (osfrb(fp, buf, 9))
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/* parse the header */
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entry_ofs = t3rp4u(buf);
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entry_siz = t3rp4u(buf + 4);
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entry_name_len = (unsigned char)buf[8];
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/* read the entry's name */
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if (osfrb(fp, buf, entry_name_len))
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/* XOR the bytes of the name with 0xFF */
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for (p = buf, rem = entry_name_len ; rem != 0 ; ++p, --rem)
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/* if this is the one we're looking for, return it */
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if (entry_name_len == resname_len
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&& memicmp(resname, buf, resname_len) == 0)
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* fill in the return information - note that the
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* entry offset given in the header is an offset from
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* data block's starting location, so fix this up to
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* an absolute seek location for the return value
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info->seek_pos = base_ofs + entry_ofs;
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info->siz = entry_siz;
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else if (memcmp(buf, "EOF ", 4) == 0)
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* end of file - we've finished without finding the resource,
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* we don't care about anything else - just skip this block
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* and keep going; to skip the block, simply seek ahead by the
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* size of the block's contents as given in the block header
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osfseek(fp, siz, OSFSK_CUR);
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/* ------------------------------------------------------------------------ */
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* Find a multimedia resource with the given name in the given file. The
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* file must be positioned at the start of the tads game file when we're
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* invoked - this allows searching for a resource within a game file that
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* is embedded in a larger file stream, since we don't care where within
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* the osfildef stream the tads game file starts.
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* Fills in the resource information structure with the seek offset and
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* size of the resource in the file and returns true if the resource is
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* found; returns false if a resource with the given name doesn't exist in
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int tads_find_resource_fp(osfildef *fp, const char *resname,
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/* read the signature */
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if (!osfrb(fp, buf, 12))
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/* seek back to the start of the header */
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osfseek(fp, -12, OSFSK_CUR);
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/* check which signature we have */
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if (memcmp(buf, T2_SIG, strlen(T2_SIG)) == 0)
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/* it's a tads 2 game file - read it accordingly */
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return t2_find_res(fp, resname, info);
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else if (memcmp(buf, T3_SIG, strlen(T3_SIG)) == 0)
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/* it's a t3 image file - read it accordingly */
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return t3_find_res(fp, resname, info);
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* if we get here, it means either that we couldn't read the
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* signature, or that we didn't recognize the signature - in either
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* case, we can't parse the file at all, so we can't find the resource
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* Find a resource in a file, given the filename.
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* Fills in the resource information structure with the seek offset and
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* size of the resource in the file and returns true if the resource is
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* found; returns false if a resource with the given name doesn't exist in
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int tads_find_resource(const char *fname, const char *resname,
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if ((fp = osfoprb(fname, OSFTGAME)) == 0
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&& (fp = osfoprb(fname, OSFTT3IMG)) == 0)
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/* we couldn't open the file, so there's no resource to be found */
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/* find the resource in the file */
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found = tads_find_resource_fp(fp, resname, info);
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/* we're done with the file - close it */
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/* return our found or not-found indication */
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/* ------------------------------------------------------------------------ */
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* Testing main - looks for a given resource in a given file, and copies
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* it to standard output if found.
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int main(int argc, char **argv)
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tads_resinfo res_info;
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fprintf(stderr, "usage: resfind <filename> <resname>\n");
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/* get the arguments */
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if ((fp = osfoprb(fname, OSFTGAME)) == 0
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&& (fp = osfoprb(fname, OSFTT3IMG)) == 0)
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fprintf(stderr, "unable to open file \"%s\"\n", fname);
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/* find the resource */
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if (!tads_find_resource_fp(fp, resname, &res_info))
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fprintf(stderr, "unable to find resource \"%s\"\n", resname);
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/* seek to the resource */
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osfseek(fp, res_info.seek_pos, OSFSK_SET);
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/* copy the resource to standard output */
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for (rem = res_info.siz ; rem != 0 ; )
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* read up to the buffer size or up to the resource size
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* remaining, whichever is smaller
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if (osfrb(fp, buf, cur))
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fprintf(stderr, "error reading %u bytes from file\n", cur);
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/* copy the chunk to standard output */
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fwrite(buf, cur, 1, stdout);
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/* deduct the amount we just read from the size remaining */
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/* done with the file - close it */
added
removed
tads/tads3/resfind.cpp
