Add a basic tiffinfo utility

Also fix a few TIFF-related issues.

tools/.gitignore

@@ -1,2 +1,3 @@
 /pnginfo
 /jpeginfo
+/tiffinfo

tools/Makefile

@@ -5,7 +5,7 @@ CFLAGS = -g -O2 -Wall -Wextra `pkg-config --cflags $(deps)`
 LDLIBS = -ljq `pkg-config --libs $(deps)`
 
 deps = libpng
-targets = pnginfo jpeginfo
+targets = pnginfo jpeginfo tiffinfo
 
 all: $(targets)
 $(targets): info.h

tools/info.h

@@ -551,14 +551,15 @@ static struct tiff_entry tiff_entries[] = {
 		{}
 	}},
 	{"ReferenceBlackWhite", 532, NULL},
+	{"XMP", 700, NULL},  // Adobe XMP Specification Part 3 Table 12/13/39
 	{"ImageID", 32781, NULL},  // Adobe PageMaker 6.0 TIFF Technical Notes
 	{"Copyright", 33432, NULL},
+	// TODO(p): Extract IPTC DataSets, like we do directly with PSIRs.
+	{"IPTC", 33723, NULL},  // Adobe XMP Specification Part 3 Table 12/39
 	// TODO(p): Extract PSIRs, like we do directly with the JPEG segment.
 	{"Photoshop", 34377, NULL},  // Adobe XMP Specification Part 3 Table 12/39
 	{"Exif IFD Pointer", 34665, NULL},  // Exif 2.3
 	{"GPS Info IFD Pointer", 34853, NULL},  // Exif 2.3
-	// TODO(p): Extract IPTC DataSets, like we do directly with PSIRs.
-	{"IPTC", 37723, NULL},  // Adobe XMP Specification Part 3 Table 12/39
 	{"ImageSourceData", 37724, NULL},  // Adobe Photoshop TIFF Technical Notes
 	{}
 };
@@ -886,8 +887,9 @@ parse_exif_subifds(struct tiffer *T, const struct tiffer_entry *entry,
 		offset < 0 || offset > UINT32_MAX || !tiffer_subifd(T, offset, &subT))
 		return jv_null();
 
-	// The chain should correspond to the values in the entry,
-	// we are not going to verify it.
+	// The chain should correspond to the values in the entry
+	// (TIFF Technical Note 1), we are not going to verify it.
+	// Note that Nikon NEFs do not follow this rule.
 	jv a = jv_array();
 	do a = jv_array_append(a, parse_exif_ifd(&subT, info));
 	while (tiffer_next_ifd(&subT));

tools/tiffinfo.c

@@ -0,0 +1,79 @@
+//
+// tiffinfo.c: acquire information about TIFF files in JSON format
+//
+// Copyright (c) 2021, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+#include "info.h"
+
+#include <jv.h>
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+// This is essentially the same as jpeginfo.c, but we only have an Exif segment.
+// TODO(p): Photoshop data and ICC profiles also have their tag,
+// they're not currently processed.
+
+static jv
+do_file(const char *filename, jv o)
+{
+	const char *err = NULL;
+	FILE *fp = fopen(filename, "rb");
+	if (!fp) {
+		err = strerror(errno);
+		goto error;
+	}
+
+	uint8_t *data = NULL, buf[256 << 10];
+	size_t n, len = 0;
+	while ((n = fread(buf, sizeof *buf, sizeof buf / sizeof *buf, fp))) {
+		data = realloc(data, len + n);
+		memcpy(data + len, buf, n);
+		len += n;
+	}
+	if (ferror(fp)) {
+		err = strerror(errno);
+		goto error_read;
+	}
+
+	o = parse_exif(o, data, len);
+
+error_read:
+	fclose(fp);
+	free(data);
+error:
+	if (err)
+		o = add_error(o, err);
+	return o;
+}
+
+int
+main(int argc, char *argv[])
+{
+	// XXX: Can't use `xargs -P0`, there's a risk of non-atomic writes.
+	// Usage: find . -iname *.png -print0 | xargs -0 ./pnginfo
+	for (int i = 1; i < argc; i++) {
+		const char *filename = argv[i];
+
+		jv o = jv_object();
+		o = jv_object_set(o, jv_string("filename"), jv_string(filename));
+		o = do_file(filename, o);
+		jv_dumpf(o, stdout, 0 /* Might consider JV_PRINT_SORTED. */);
+		fputc('\n', stdout);
+	}
+	return 0;
+}