From ca1aea390ba0b108033b64de0b972c694f2b0df8 Mon Sep 17 00:00:00 2001
From: Curtis McEnroe <june@causal.agency>
Date: Wed, 14 Nov 2018 17:11:34 -0500
Subject: Remove zlib dependency from png.h

---
 bin/png.h | 92 +++++++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 54 insertions(+), 38 deletions(-)

diff --git a/bin/png.h b/bin/png.h
index 05993f87..4eb4da1f 100644
--- a/bin/png.h
+++ b/bin/png.h
@@ -14,79 +14,95 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <arpa/inet.h>
 #include <err.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sysexits.h>
-#include <zlib.h>
 
-enum {
-	PNGGrayscale,
-	PNGTruecolor = 2,
-	PNGIndexed,
-	PNGAlpha,
-};
-
-enum {
-	PNGNone,
-	PNGSub,
-	PNGUp,
-	PNGAverage,
-	PNGPaeth,
-};
+static inline uint32_t pngCRCTable(uint8_t n) {
+	static uint32_t table[256];
+	if (table[1]) return table[n];
+	for (int i = 0; i < 256; ++i) {
+		table[i] = i;
+		for (int j = 0; j < 8; ++j) {
+			table[i] = (table[i] >> 1) ^ (table[i] & 1 ? 0xEDB88320 : 0);
+		}
+	}
+	return table[n];
+}
 
 static uint32_t pngCRC;
-static inline void pngWrite(FILE *file, const void *ptr, size_t len) {
+
+static inline void pngWrite(FILE *file, const uint8_t *ptr, uint32_t len) {
 	if (!fwrite(ptr, len, 1, file)) err(EX_IOERR, "pngWrite");
-	pngCRC = crc32(pngCRC, ptr, len);
+	for (uint32_t i = 0; i < len; ++i) {
+		pngCRC = pngCRCTable(pngCRC ^ ptr[i]) ^ (pngCRC >> 8);
+	}
 }
 static inline void pngInt32(FILE *file, uint32_t n) {
-	n = htonl(n);
-	pngWrite(file, &n, 4);
+	pngWrite(file, (uint8_t []) { n >> 24, n >> 16, n >> 8, n }, 4);
 }
 static inline void pngChunk(FILE *file, char type[static 4], uint32_t len) {
 	pngInt32(file, len);
-	pngCRC = crc32(0, Z_NULL, 0);
-	pngWrite(file, type, 4);
+	pngCRC = ~0;
+	pngWrite(file, (uint8_t *)type, 4);
 }
 
+enum {
+	PNGGrayscale,
+	PNGTruecolor = 2,
+	PNGIndexed,
+	PNGAlpha,
+};
+
 static inline void pngHead(
 	FILE *file, uint32_t width, uint32_t height, uint8_t depth, uint8_t color
 ) {
-	pngWrite(file, "\x89PNG\r\n\x1A\n", 8);
+	pngWrite(file, (uint8_t *)"\x89PNG\r\n\x1A\n", 8);
 	pngChunk(file, "IHDR", 13);
 	pngInt32(file, width);
 	pngInt32(file, height);
 	pngWrite(file, &depth, 1);
 	pngWrite(file, &color, 1);
-	pngWrite(file, "\0\0\0", 3);
-	pngInt32(file, pngCRC);
+	pngWrite(file, (uint8_t []) { 0, 0, 0 }, 3);
+	pngInt32(file, ~pngCRC);
 }
 
 static inline void pngPalette(FILE *file, const uint8_t *pal, uint32_t len) {
 	pngChunk(file, "PLTE", len);
 	pngWrite(file, pal, len);
-	pngInt32(file, pngCRC);
+	pngInt32(file, ~pngCRC);
 }
 
-static inline void pngData(FILE *file, const uint8_t *data, uint32_t len) {
-	uLong zlen = compressBound(len);
-	uint8_t *zdata = malloc(zlen);
-	if (!zlen) err(EX_OSERR, "malloc");
-
-	int error = compress(zdata, &zlen, data, len);
-	if (error != Z_OK) errx(EX_SOFTWARE, "compress: %d", error);
+enum {
+	PNGNone,
+	PNGSub,
+	PNGUp,
+	PNGAverage,
+	PNGPaeth,
+};
 
+static inline void pngData(FILE *file, const uint8_t *data, uint32_t len) {
+	uint32_t adler1 = 1, adler2 = 0;
+	for (uint32_t i = 0; i < len; ++i) {
+		adler1 = (adler1 + data[i]) % 65521;
+		adler2 = (adler1 + adler2) % 65521;
+	}
+	uint32_t zlen = 2 + 5 * ((len + 0xFFFE) / 0xFFFF) + len + 4;
 	pngChunk(file, "IDAT", zlen);
-	pngWrite(file, zdata, zlen);
-	pngInt32(file, pngCRC);
-
-	free(zdata);
+	pngWrite(file, (uint8_t []) { 0x08, 0x1D }, 2);
+	for (; len > 0xFFFF; data += 0xFFFF, len -= 0xFFFF) {
+		pngWrite(file, (uint8_t []) { 0x00, 0xFF, 0xFF, 0x00, 0x00 }, 5);
+		pngWrite(file, data, 0xFFFF);
+	}
+	pngWrite(file, (uint8_t []) { 0x01, len, len >> 8, ~len, ~len >> 8 }, 5);
+	pngWrite(file, data, len);
+	pngInt32(file, adler2 << 16 | adler1);
+	pngInt32(file, ~pngCRC);
 }
 
 static inline void pngTail(FILE *file) {
 	pngChunk(file, "IEND", 0);
-	pngInt32(file, pngCRC);
+	pngInt32(file, ~pngCRC);
 }
-- 
cgit 1.4.1