342 lines
9.2 KiB
C
342 lines
9.2 KiB
C
/*
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PB8 compressor and decompressor
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Copyright 2019 Damian Yerrick
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <stdbool.h>
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#include <assert.h>
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// For setting stdin/stdout to binary mode
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#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
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#include <unistd.h>
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#define fd_isatty isatty
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#elif defined (_WIN32)
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#include <io.h>
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#include <fcntl.h>
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#define fd_isatty _isatty
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#endif
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/*
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; The logo is compressed using PB8, a form of RLE with unary-coded
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; run lengths. Each block representing 8 bytes consists of a control
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; byte, where each bit (MSB to LSB) is 0 for literal or 1 for repeat
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; previous, followed by the literals in that block.
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SameBoyLogo_dst = $8080
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SameBoyLogo_length = (128 * 24) / 64
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LoadTileset:
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ld hl, SameBoyLogo
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ld de, SameBoyLogo_dst
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ld c, SameBoyLogo_length
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.pb8BlockLoop:
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; Register map for PB8 decompression
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; HL: source address in boot ROM
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; DE: destination address in VRAM
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; A: Current literal value
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; B: Repeat bits, terminated by 1000...
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; C: Number of 8-byte blocks left in this block
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; Source address in HL lets the repeat bits go straight to B,
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; bypassing A and avoiding spilling registers to the stack.
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ld b, [hl]
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inc hl
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; Shift a 1 into lower bit of shift value. Once this bit
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; reaches the carry, B becomes 0 and the byte is over
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scf
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rl b
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.pb8BitLoop:
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; If not a repeat, load a literal byte
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jr c,.pb8Repeat
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ld a, [hli]
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.pb8Repeat:
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; Decompressed data uses colors 0 and 1, so write once, inc twice
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ld [de], a
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inc de
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inc de
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sla b
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jr nz, .pb8BitLoop
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dec c
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jr nz, .pb8BlockLoop
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ret
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*/
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/* Compressor and decompressor *************************************/
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/**
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* Compresses an input stream to PB8 data on an output stream.
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* @param infp input stream
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* @param outfp output stream
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* @param blocklength size of an independent input block in bytes
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* @return 0 for reaching infp end of file, or EOF for error
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*/
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int pb8(FILE *infp, FILE *outfp, size_t blocklength)
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{
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blocklength >>= 3; // convert bytes to blocks
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assert(blocklength > 0);
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while (1) {
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int last_byte = EOF; // value that never occurs in a file
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for (size_t blkleft = blocklength; blkleft > 0; --blkleft) {
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unsigned int control_byte = 0x0001;
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unsigned char literals[8];
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size_t nliterals = 0;
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while (control_byte < 0x100) {
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int c = fgetc(infp);
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if (c == EOF) break;
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control_byte <<= 1;
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if (c == last_byte) {
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control_byte |= 0x01;
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}
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else {
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literals[nliterals++] = last_byte = c;
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}
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}
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if (control_byte > 1) {
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// Fill partial block with repeats
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while (control_byte < 0x100) {
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control_byte = (control_byte << 1) | 1;
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}
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// Write control byte and check for write failure
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int ok = fputc(control_byte & 0xFF, outfp);
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if (ok == EOF) return EOF;
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size_t ok2 = fwrite(literals, 1, nliterals, outfp);
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if (ok2 < nliterals) return EOF;
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}
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// If finished, return success or failure
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if (ferror(infp) || ferror(outfp)) return EOF;
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if (feof(infp)) return 0;
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} // End 8-byte block
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} // End packet, resetting last_byte
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}
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/**
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* Decompresses PB8 data on an input stream to an output stream.
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* @param infp input stream
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* @param outfp output stream
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* @return 0 for reaching infp end of file, or EOF for error
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*/
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int unpb8(FILE *infp, FILE *outfp)
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{
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int last_byte = 0;
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while (1) {
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int control_byte = fgetc(infp);
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if (control_byte == EOF) {
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return feof(infp) ? 0 : EOF;
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}
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control_byte &= 0xFF;
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for (size_t bytesleft = 8; bytesleft > 0; --bytesleft) {
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if (!(control_byte & 0x80)) {
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last_byte = fgetc(infp);
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if (last_byte == EOF) return EOF; // read error
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}
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control_byte <<= 1;
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int ok = fputc(last_byte, outfp);
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if (ok == EOF) return EOF;
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}
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}
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}
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/* CLI frontend ****************************************************/
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static inline void set_fd_binary(unsigned int fd)
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{
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#ifdef _WIN32
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_setmode(fd, _O_BINARY);
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#else
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(void) fd;
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#endif
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}
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static const char *usage_msg =
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"usage: pb8 [-d] [-l blocklength] [infile [outfile]]\n"
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"Compresses a file using RLE with unary run and literal lengths.\n"
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"\n"
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"options:\n"
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" -d decompress\n"
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" -l blocklength allow RLE packets to span up to blocklength\n"
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" input bytes (multiple of 8; default 8)\n"
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" -h, -?, --help show this usage page\n"
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" --version show copyright info\n"
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"\n"
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"If infile is - or missing, it is standard input.\n"
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"If outfile is - or missing, it is standard output.\n"
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"You cannot compress to or decompress from a terminal.\n"
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;
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static const char *version_msg =
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"PB8 compressor (C version) v0.01\n"
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"Copyright 2019 Damian Yerrick <https://pineight.com/contact/>\n"
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"This software is provided 'as-is', without any express or implied\n"
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"warranty.\n"
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;
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static const char *toomanyfilenames_msg =
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"pb8: too many filenames; try pb8 --help\n";
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int main(int argc, char **argv)
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{
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const char *infilename = NULL;
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const char *outfilename = NULL;
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bool decompress = false;
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size_t blocklength = 8;
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for (int i = 1; i < argc; ++i) {
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if (argv[i][0] == '-' && argv[i][1] != 0) {
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if (!strcmp(argv[i], "--help")) {
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fputs(usage_msg, stdout);
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return 0;
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}
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if (!strcmp(argv[i], "--version")) {
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fputs(version_msg, stdout);
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return 0;
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}
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// -t1 or -t 1
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int argtype = argv[i][1];
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switch (argtype) {
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case 'h':
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case '?':
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fputs(usage_msg, stdout);
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return 0;
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case 'd':
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decompress = true;
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break;
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case 'l': {
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const char *argvalue = argv[i][2] ? argv[i] + 2 : argv[++i];
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const char *endptr = NULL;
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unsigned long tvalue = strtoul(argvalue, (char **)&endptr, 10);
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if (endptr == argvalue || tvalue == 0 || tvalue > SIZE_MAX) {
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fprintf(stderr, "pb8: block length %s not a positive integer\n",
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argvalue);
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return EXIT_FAILURE;
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}
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if (tvalue % 8 != 0) {
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fprintf(stderr, "pb8: block length %s not a multiple of 8\n",
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argvalue);
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return EXIT_FAILURE;
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}
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blocklength = tvalue;
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} break;
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default:
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fprintf(stderr, "pb8: unknown option -%c\n", argtype);
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return EXIT_FAILURE;
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}
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}
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else if (!infilename) {
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infilename = argv[i];
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}
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else if (!outfilename) {
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outfilename = argv[i];
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}
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else {
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fputs(toomanyfilenames_msg, stderr);
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return EXIT_FAILURE;
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}
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}
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if (infilename && !strcmp(infilename, "-")) {
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infilename = NULL;
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}
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if (!infilename && decompress && fd_isatty(0)) {
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fputs("pb8: cannot decompress from terminal; try redirecting stdin\n",
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stderr);
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return EXIT_FAILURE;
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}
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if (outfilename && !strcmp(outfilename, "-")) {
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outfilename = NULL;
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}
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if (!outfilename && !decompress && fd_isatty(1)) {
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fputs("pb8: cannot compress to terminal; try redirecting stdout or pb8 --help\n",
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stderr);
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return EXIT_FAILURE;
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}
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FILE *infp = NULL;
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if (infilename) {
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infp = fopen(infilename, "rb");
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if (!infp) {
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fprintf(stderr, "pb8: error opening %s ", infilename);
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perror("for reading");
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return EXIT_FAILURE;
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}
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}
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else {
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infp = stdin;
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set_fd_binary(0);
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}
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FILE *outfp = NULL;
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if (outfilename) {
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outfp = fopen(outfilename, "wb");
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if (!outfp) {
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fprintf(stderr, "pb8: error opening %s ", outfilename);
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perror("for writing");
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fclose(infp);
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return EXIT_FAILURE;
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}
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}
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else {
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outfp = stdout;
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set_fd_binary(1);
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}
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int compfailed = 0;
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int has_ferror = 0;
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if (decompress) {
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compfailed = unpb8(infp, outfp);
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}
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else {
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compfailed = pb8(infp, outfp, blocklength);
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}
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fflush(outfp);
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if (ferror(infp)) {
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fprintf(stderr, "pb8: error reading %s\n",
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infilename ? infilename : "<stdin>");
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has_ferror = EOF;
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}
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fclose(infp);
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if (ferror(outfp)) {
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fprintf(stderr, "pb8: error writing %s\n",
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outfilename ? outfilename : "<stdout>");
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has_ferror = EOF;
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}
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fclose(outfp);
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if (compfailed && !has_ferror) {
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fputs("pb8: unknown compression failure\n", stderr);
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}
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return (compfailed || has_ferror) ? EXIT_FAILURE : EXIT_SUCCESS;
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}
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