127 lines
3.0 KiB
C
127 lines
3.0 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#define CHUNK (1024 * 1024) // 1 MB buffer
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#define MAX_PDF_SIZE (100LL * 1024 * 1024)
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typedef enum {
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SCANNING,
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IN_PDF
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} State;
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static int valid_pdf_header(const unsigned char *p, size_t len) {
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if (len < 10) return 0;
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if (p[0] != '%' || p[1] != 'P' || p[2] != 'D' || p[3] != 'F' || p[4] != '-')
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return 0;
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if (p[5] < '0' || p[5] > '9') return 0;
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if (p[6] != '.') return 0;
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if (p[7] < '0' || p[7] > '9') return 0;
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size_t i = 8;
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if (p[i] >= '0' && p[i] <= '9') i++;
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return (p[i] == '\n' || (p[i] == '\r' && p[i + 1] == '\n'));
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}
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static void make_outfile(char *path, size_t sz, const char *dir, int idx) {
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snprintf(path, sz, "%s/pdf_%04d.pdf", dir, idx);
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}
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int main(int argc, char **argv) {
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if (argc != 3) {
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fprintf(stderr, "Usage: %s <image_file> <output_dir>\n", argv[0]);
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return 1;
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}
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char *infile = argv[1];
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if (infile[0] == '-' && infile[1] == '\0') {
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infile = "/dev/stdin";
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}
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const char *outdir = argv[2];
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mkdir(outdir, 0755);
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FILE *in = fopen(infile, "rb");
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if (!in) {
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perror("open input");
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return 1;
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}
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unsigned char *buf = malloc(CHUNK);
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if (!buf) return 1;
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State state = SCANNING;
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FILE *out = NULL;
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unsigned char eof_win[5] = {0}; // rolling "%%EOF"
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size_t pdf_size = 0;
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int pdf_count = 0;
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// overlap buffer to catch split headers across chunks
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unsigned char overlap[16];
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size_t overlap_len = 0;
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while (1) {
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size_t r = fread(buf, 1, CHUNK, in);
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if (r == 0) break;
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size_t i = 0;
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// prepend overlap
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unsigned char *data = buf;
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size_t len = r;
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unsigned char temp[CHUNK + 16];
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if (overlap_len > 0) {
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memcpy(temp, overlap, overlap_len);
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memcpy(temp + overlap_len, buf, r);
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data = temp;
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len = r + overlap_len;
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i = 0;
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}
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overlap_len = 0;
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for (; i < len; i++) {
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if (state == SCANNING) {
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// only attempt match on '%'
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if (data[i] == '%' && i + 10 < len) {
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if (valid_pdf_header(&data[i], len - i)) {
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char path[512];
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make_outfile(path, sizeof(path), outdir, pdf_count++);
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out = fopen(path, "wb");
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if (!out) {
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state = SCANNING;
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continue;
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}
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state = IN_PDF;
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pdf_size = 0;
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memset(eof_win, 0, sizeof(eof_win));
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}
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}
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}
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else if (state == IN_PDF) {
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if (pdf_size >= MAX_PDF_SIZE) {
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fclose(out);
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out = NULL;
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state = SCANNING;
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continue;
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}
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fputc(data[i], out);
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pdf_size++;
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// rolling EOF detector
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eof_win[0] = eof_win[1];
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eof_win[1] = eof_win[2];
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eof_win[2] = eof_win[3];
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eof_win[3] = eof_win[4];
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eof_win[4] = data[i];
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if (eof_win[0] == '%' &&
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eof_win[1] == '%' &&
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eof_win[2] == 'E' &&
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eof_win[3] == 'O' &&
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eof_win[4] == 'F') {
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fclose(out);
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out = NULL;
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state = SCANNING;
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}
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}
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}
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// save last 16 bytes for boundary-safe matching
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overlap_len = (len < 16) ? len : 16;
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memcpy(overlap, data + (len - overlap_len), overlap_len);
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}
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if (out) fclose(out);
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free(buf);
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fclose(in);
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return 0;
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}
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