From 11aa9d37b0c06b678a27db8e37d4dc817dead4bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tim=20D=C3=BCsterhus?= <tim@tideways-gmbh.com>
Date: Mon, 3 Nov 2025 16:57:39 +0100
Subject: [PATCH] pack: Support endian specifier

---
 ext/standard/pack.c | 59 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 51 insertions(+), 8 deletions(-)

diff --git a/ext/standard/pack.c b/ext/standard/pack.c
index 55da64897a2..5be2c0260bc 100644
--- a/ext/standard/pack.c
+++ b/ext/standard/pack.c
@@ -30,6 +30,7 @@
 	outputpos += (a)*(b);
 
 typedef enum {
+	PHP_DEFAULT_ENDIAN,
 	PHP_LITTLE_ENDIAN,
 	PHP_BIG_ENDIAN,
 } php_pack_endianness;
@@ -193,6 +194,11 @@ static double php_pack_parse_double(int is_little_endian, void * src)
 }
 /* }}} */
 
+struct formatarg {
+	int count;
+	php_pack_endianness endianness;
+};
+
 /* pack() idea stolen from Perl (implemented formats behave the same as there except J and P)
  * Implemented formats are Z, A, a, h, H, c, C, s, S, i, I, l, L, n, N, q, Q, J, P, f, d, x, X, @.
  * Added g, G for little endian float and big endian float, added e, E for little endian double and big endian double.
@@ -207,7 +213,7 @@ PHP_FUNCTION(pack)
 	char *format;
 	size_t formatlen;
 	char *formatcodes;
-	int *formatargs;
+	struct formatarg *formatargs;
 	size_t formatcount = 0;
 	int outputpos = 0, outputsize = 0;
 	zend_string *output;
@@ -226,9 +232,11 @@ PHP_FUNCTION(pack)
 	for (i = 0; i < formatlen; formatcount++) {
 		char code = format[i++];
 		int arg = 1;
+		php_pack_endianness endianness = PHP_DEFAULT_ENDIAN;
 
 		/* Handle format arguments if any */
 		if (i < formatlen) {
+ again:;
 			char c = format[i];
 
 			if (c == '*') {
@@ -242,6 +250,11 @@ PHP_FUNCTION(pack)
 					i++;
 				}
 			}
+			else if (c == '<' || c == '>') {
+				endianness = c == '<' ? PHP_LITTLE_ENDIAN : PHP_BIG_ENDIAN;
+				i++;
+				goto again;
+			}
 		}
 
 		/* Handle special arg '*' for all codes and check argv overflows */
@@ -341,8 +354,20 @@ PHP_FUNCTION(pack)
 				RETURN_THROWS();
 		}
 
+		if (endianness != PHP_DEFAULT_ENDIAN) {
+			if (strchr("sSiIlLqQf", code) == NULL) {
+				efree(formatcodes);
+				efree(formatargs);
+				zend_value_error("Type %c: Endianness may not be specified", code);
+				RETURN_THROWS();
+			}
+		}
+
 		formatcodes[formatcount] = code;
-		formatargs[formatcount] = arg;
+		formatargs[formatcount] = (struct formatarg){
+			.count = arg,
+			.endianness = endianness,
+		};
 	}
 
 	if (currentarg < num_args) {
@@ -352,7 +377,7 @@ PHP_FUNCTION(pack)
 	/* Calculate output length and upper bound while processing*/
 	for (i = 0; i < formatcount; i++) {
 		char code = formatcodes[i];
-		int arg = formatargs[i];
+		int arg = formatargs[i].count;
 
 		switch (code) {
 			case 'h':
@@ -435,7 +460,7 @@ PHP_FUNCTION(pack)
 	/* Do actual packing */
 	for (i = 0; i < formatcount; i++) {
 		char code = formatcodes[i];
-		int arg = formatargs[i];
+		int arg = formatargs[i].count;
 
 		switch (code) {
 			case 'a':
@@ -517,6 +542,10 @@ PHP_FUNCTION(pack)
 					endianness = PHP_LITTLE_ENDIAN;
 				}
 
+				if (formatargs[i].endianness != PHP_DEFAULT_ENDIAN) {
+					endianness = formatargs[i].endianness;
+				}
+
 				while (arg-- > 0) {
 					php_pack(&argv[currentarg++], 2, endianness, &ZSTR_VAL(output)[outputpos]);
 					outputpos += 2;
@@ -525,12 +554,18 @@ PHP_FUNCTION(pack)
 			}
 
 			case 'i':
-			case 'I':
+			case 'I': {
+				php_pack_endianness endianness = PHP_MACHINE_ENDIAN;
+				if (formatargs[i].endianness != PHP_DEFAULT_ENDIAN) {
+					endianness = formatargs[i].endianness;
+				}
+
 				while (arg-- > 0) {
-					php_pack(&argv[currentarg++], sizeof(int), PHP_MACHINE_ENDIAN, &ZSTR_VAL(output)[outputpos]);
+					php_pack(&argv[currentarg++], sizeof(int), endianness, &ZSTR_VAL(output)[outputpos]);
 					outputpos += sizeof(int);
 				}
 				break;
+			}
 
 			case 'l':
 			case 'L':
@@ -543,6 +578,9 @@ PHP_FUNCTION(pack)
 				} else if (code == 'V') {
 					endianness = PHP_LITTLE_ENDIAN;
 				}
+				if (formatargs[i].endianness != PHP_DEFAULT_ENDIAN) {
+					endianness = formatargs[i].endianness;
+				}
 
 				while (arg-- > 0) {
 					php_pack(&argv[currentarg++], 4, endianness, &ZSTR_VAL(output)[outputpos]);
@@ -573,6 +611,11 @@ PHP_FUNCTION(pack)
 #endif
 
 			case 'f': {
+				if (formatargs[i].endianness == PHP_LITTLE_ENDIAN) {
+					goto g;
+				} else if (formatargs[i].endianness == PHP_BIG_ENDIAN) {
+					goto G;
+				}
 				while (arg-- > 0) {
 					float v = (float) zval_get_double(&argv[currentarg++]);
 					memcpy(&ZSTR_VAL(output)[outputpos], &v, sizeof(v));
@@ -582,7 +625,7 @@ PHP_FUNCTION(pack)
 			}
 
 			case 'g': {
-				/* pack little endian float */
+ g:				/* pack little endian float */
 				while (arg-- > 0) {
 					float v = (float) zval_get_double(&argv[currentarg++]);
 					php_pack_copy_float(1, &ZSTR_VAL(output)[outputpos], v);
@@ -592,7 +635,7 @@ PHP_FUNCTION(pack)
 				break;
 			}
 			case 'G': {
-				/* pack big endian float */
+ G:				/* pack big endian float */
 				while (arg-- > 0) {
 					float v = (float) zval_get_double(&argv[currentarg++]);
 					php_pack_copy_float(0, &ZSTR_VAL(output)[outputpos], v);
-- 
2.43.0