v1.0.1: better timestamp in Windows build

Makefile

@@ -92,7 +92,10 @@ png2webp: png2webp.c libpng/png.c libpng/pngerror.c libpng/pngget.c \
 	libwebp/src/utils/quant_levels_utils.c \
 	libwebp/src/utils/random_utils.c libwebp/src/utils/rescaler_utils.c \
 	libwebp/src/utils/thread_utils.c libwebp/src/utils/utils.c
+petimestamp: petimestamp.c
+png2webp_timestamped: png2webp petimestamp
+	./petimestamp png2webp.exe ${shell git show -s --format=%ct}
 install: png2webp
 	${INSTALL} $^ ${DESTDIR}${PREFIX}/bin/
 clean:
-	${RM} png2webp
+	${RM} png2webp petimestamp

petimestamp.c

@@ -0,0 +1,63 @@
+// anti-copyright Lucy Phipps 2022
+// vi: sw=2 tw=80
+#include <assert.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <stdio.h>
+static uint32_t le32(uint8_t x[4]) {
+  return (uint32_t)((x[3] << 24) | (x[2] << 16) | (x[1] << 8) | x[0]);
+}
+int main(int argc, char **argv) {
+  static_assert(CHAR_BIT == 8, "char isn't 8-bit");
+  if(argc != 3) {
+    fputs("Usage: petimestamp <file> <timestamp>\n", stderr);
+    return -1;
+  }
+  char *end;
+  uintmax_t t = strtoumax(argv[2], &end, 0);
+  if(t > 0xFFFFFFFF || *end) {
+    fputs("Invalid timestamp!\n"
+	  "Should be decimal, octal (leading 0), or hexadecimal (leading 0x),\n"
+	  "as seconds since the epoch, in range 0 to 0xFFFFFFFF\n",
+      stderr);
+    return 1;
+  }
+  FILE *f = fopen(argv[1], "r+b");
+  if(!f) {
+    fputs("Couldn't open file\n", stderr);
+    return 1;
+  }
+  char dos[2];
+  if(!fread(dos, 2, 1, f)) {
+  bad:
+    fputs("Invalid Windows PE(64) file\n", stderr);
+    fclose(f);
+    return 1;
+  }
+  if(*dos != 'M' || dos[1] != 'Z') goto bad;
+  if(fseek(f, 60, SEEK_SET)) goto bad;
+  uint8_t buf[4];
+  if(!fread(buf, 4, 1, f)) goto bad;
+  uint32_t offset = le32(buf);
+  if(fseek(f, offset, SEEK_SET)) goto bad;
+  if(!fread(buf, 4, 1, f)) goto bad;
+  if(*buf != 'P' || buf[1] != 'E' || buf[2] || buf[3]) goto bad;
+  if(fseek(f, offset + 8, SEEK_SET)) goto bad;
+#ifndef NO_PRINT_ORIG
+  if(!fread(buf, 4, 1, f)) goto bad;
+  uint32_t origts = le32(buf);
+  fprintf(stderr, "Original timestamp: %" PRIu32 "\n", origts);
+  if(fseek(f, offset + 8, SEEK_SET)) goto bad;
+#endif
+  if(!fwrite(
+       (char[4]){(char)t, (char)(t >> 8), (char)(t >> 16), (char)(t >> 24)}, 4,
+       1, f)) {
+    fputs("Couldn't write new timestamp\n", stderr);
+    fclose(f);
+    return 1;
+  }
+  if(fclose(f)) {
+    fputs("Error while closing file\n", stderr);
+    return 1;
+  }
+}

png2webp.c

@@ -1,6 +1,6 @@
 // anti-copyright Lucy Phipps 2022
 // vi: sw=2 tw=80
-#define VERSION "v1.0"
+#define VERSION "v1.0.1"
 #include <assert.h>
 #include <errno.h>
 #include <limits.h>