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Fix GH-17068: Add pack()/unpack() format for signed integer endianness #19368

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Fix GH-17068: Add pack()/unpack() format for signed integer endianness #19368

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6 changes: 6 additions & 0 deletions NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,12 @@ PHP NEWS
. Fixed bug GH-17927 (Reflection: have some indication of property hooks in
`_property_string()`). (DanielEScherzer)

- Standard:
. Added pack()/unpack() support for signed integers with specific endianness.
New format codes: m/y for signed 2-byte (little/big endian), M/Y for signed
4-byte (little/big endian), p/j for signed 8-byte (little/big endian).
Fixes GH-17068. (alexandre-daubois)

31 Jul 2025, PHP 8.5.0alpha4

- Core:
Expand Down
3 changes: 3 additions & 0 deletions UPGRADING
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Expand Up @@ -263,6 +263,9 @@ PHP 8.5 UPGRADE NOTES
and the function returns false. Previously, these errors were silently
ignored. This change affects only the sendmail transport.
. getimagesize() now supports HEIF/HEIC images.
. pack() and unpack() now support signed integers with specific endianness.
New format codes: m/y for signed 2-byte (little/big endian), M/Y for signed
4-byte (little/big endian), p/j for signed 8-byte (little/big endian).

- Standard:
. getimagesize() now supports SVG images when ext-libxml is also loaded.
Expand Down
82 changes: 72 additions & 10 deletions ext/standard/pack.c
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Expand Up @@ -196,6 +196,7 @@ static double php_pack_parse_double(int is_little_endian, void * src)
/* 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.
* Added m, y for little/big endian signed 2-byte, M, Y for little/big endian signed 4-byte, p, j for little/big endian signed 8-byte.
*/
/* {{{ Takes one or more arguments and packs them into a binary string according to the format argument */
PHP_FUNCTION(pack)
Expand Down Expand Up @@ -293,6 +294,8 @@ PHP_FUNCTION(pack)
case 'Q':
case 'J':
case 'P':
case 'j':
case 'p':
#if SIZEOF_ZEND_LONG < 8
efree(formatcodes);
efree(formatargs);
Expand All @@ -317,6 +320,10 @@ PHP_FUNCTION(pack)
case 'd': /* double */
case 'e': /* little endian double */
case 'E': /* big endian double */
case 'm': /* little endian signed 2-byte */
case 'y': /* big endian signed 2-byte */
case 'M': /* little endian signed 4-byte */
case 'Y': /* big endian signed 4-byte */
if (arg < 0) {
arg = num_args - currentarg;
}
Expand Down Expand Up @@ -373,6 +380,8 @@ PHP_FUNCTION(pack)
case 'S':
case 'n':
case 'v':
case 'm': /* little endian signed 2-byte */
case 'y': /* big endian signed 2-byte */
INC_OUTPUTPOS(arg,2) /* 16 bit per arg */
break;

Expand All @@ -385,6 +394,8 @@ PHP_FUNCTION(pack)
case 'L':
case 'N':
case 'V':
case 'M': /* little endian signed 4-byte */
case 'Y': /* big endian signed 4-byte */
INC_OUTPUTPOS(arg,4) /* 32 bit per arg */
break;

Expand All @@ -393,7 +404,9 @@ PHP_FUNCTION(pack)
case 'Q':
case 'J':
case 'P':
INC_OUTPUTPOS(arg,8) /* 32 bit per arg */
case 'j':
case 'p':
INC_OUTPUTPOS(arg,8) /* 64 bit per arg */
break;
#endif

Expand Down Expand Up @@ -508,12 +521,14 @@ PHP_FUNCTION(pack)
case 's':
case 'S':
case 'n':
case 'v': {
case 'v':
case 'm':
case 'y': {
php_pack_endianness endianness = PHP_MACHINE_ENDIAN;

if (code == 'n') {
if (code == 'n' || code == 'y') {
endianness = PHP_BIG_ENDIAN;
} else if (code == 'v') {
} else if (code == 'v' || code == 'm') {
endianness = PHP_LITTLE_ENDIAN;
}

Expand All @@ -535,12 +550,14 @@ PHP_FUNCTION(pack)
case 'l':
case 'L':
case 'N':
case 'V': {
case 'V':
case 'M':
case 'Y': {
php_pack_endianness endianness = PHP_MACHINE_ENDIAN;

if (code == 'N') {
if (code == 'N' || code == 'Y') {
endianness = PHP_BIG_ENDIAN;
} else if (code == 'V') {
} else if (code == 'V' || code == 'M') {
endianness = PHP_LITTLE_ENDIAN;
}

Expand All @@ -555,12 +572,14 @@ PHP_FUNCTION(pack)
case 'q':
case 'Q':
case 'J':
case 'P': {
case 'P':
case 'j':
case 'p': {
php_pack_endianness endianness = PHP_MACHINE_ENDIAN;

if (code == 'J') {
if (code == 'J' || code == 'j') {
endianness = PHP_BIG_ENDIAN;
} else if (code == 'P') {
} else if (code == 'P' || code == 'p') {
endianness = PHP_LITTLE_ENDIAN;
}

Expand Down Expand Up @@ -672,6 +691,7 @@ PHP_FUNCTION(pack)
* f and d will return doubles.
* 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.
* Added m, y for little/big endian signed 2-byte, M, Y for little/big endian signed 4-byte, p, j for little/big endian signed 8-byte.
*/
/* {{{ Unpack binary string into named array elements according to format argument */
PHP_FUNCTION(unpack)
Expand Down Expand Up @@ -793,6 +813,8 @@ PHP_FUNCTION(unpack)
case 'S':
case 'n':
case 'v':
case 'm':
case 'y':
size = 2;
break;

Expand All @@ -807,6 +829,8 @@ PHP_FUNCTION(unpack)
case 'L':
case 'N':
case 'V':
case 'M':
case 'Y':
size = 4;
break;

Expand All @@ -815,6 +839,8 @@ PHP_FUNCTION(unpack)
case 'Q':
case 'J':
case 'P':
case 'p':
case 'j':
#if SIZEOF_ZEND_LONG > 4
size = 8;
break;
Expand Down Expand Up @@ -1017,6 +1043,18 @@ PHP_FUNCTION(unpack)
break;
}

case 'm': /* signed little endian 2-byte */
case 'y': { /* signed big endian 2-byte */
uint16_t x = *((unaligned_uint16_t*) &input[inputpos]);

if ((type == 'y' && MACHINE_LITTLE_ENDIAN) || (type == 'm' && !MACHINE_LITTLE_ENDIAN)) {
x = php_pack_reverse_int16(x);
}

ZVAL_LONG(&val, (int16_t) x);
break;
}

case 'i': /* signed integer, machine size, machine endian */
case 'I': { /* unsigned integer, machine size, machine endian */
zend_long v;
Expand Down Expand Up @@ -1051,6 +1089,18 @@ PHP_FUNCTION(unpack)
break;
}

case 'M': /* signed little endian 4-byte */
case 'Y': { /* signed big endian 4-byte */
uint32_t x = *((unaligned_uint32_t*) &input[inputpos]);

if ((type == 'Y' && MACHINE_LITTLE_ENDIAN) || (type == 'M' && !MACHINE_LITTLE_ENDIAN)) {
x = php_pack_reverse_int32(x);
}

ZVAL_LONG(&val, (int32_t) x);
break;
}

#if SIZEOF_ZEND_LONG > 4
case 'q': /* signed machine endian */
case 'Q': /* unsigned machine endian */
Expand All @@ -1070,6 +1120,18 @@ PHP_FUNCTION(unpack)
ZVAL_LONG(&val, v);
break;
}

case 'j': /* signed big endian */
case 'p': { /* signed little endian */
uint64_t x = *((unaligned_uint64_t*) &input[inputpos]);

if ((type == 'j' && MACHINE_LITTLE_ENDIAN) || (type == 'p' && !MACHINE_LITTLE_ENDIAN)) {
x = php_pack_reverse_int64(x);
}

ZVAL_LONG(&val, (int64_t) x);
break;
}
#endif

case 'f': /* float */
Expand Down
0 ext/standard/tests/strings/pack.phpt → ext/standard/tests/pack/pack.phpt
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0 ext/standard/tests/strings/pack64.phpt → ext/standard/tests/pack/pack64.phpt
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26 changes: 26 additions & 0 deletions ext/standard/tests/strings/pack64_32.phpt → ext/standard/tests/pack/pack64_32.phpt
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Expand Up @@ -50,6 +50,28 @@ try {
echo $e->getMessage(), "\n";
}

try {
var_dump(pack("p", 0));
} catch (ValueError $e) {
echo $e->getMessage(), "\n";
}
try {
var_dump(pack("j", 0));
} catch (ValueError $e) {
echo $e->getMessage(), "\n";
}

try {
var_dump(unpack("p", ''));
} catch (ValueError $e) {
echo $e->getMessage(), "\n";
}
try {
var_dump(unpack("j", ''));
} catch (ValueError $e) {
echo $e->getMessage(), "\n";
}

?>
--EXPECT--
64-bit format codes are not available for 32-bit versions of PHP
Expand All @@ -60,3 +82,7 @@ try {
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
64-bit format codes are not available for 32-bit versions of PHP
0 ext/standard/tests/strings/pack_A.phpt → ext/standard/tests/pack/pack_A.phpt
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0 ext/standard/tests/strings/pack_Z.phpt → ext/standard/tests/pack/pack_Z.phpt
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0 ext/standard/tests/strings/pack_arrays.phpt → ext/standard/tests/pack/pack_arrays.phpt
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0 ext/standard/tests/strings/pack_float.phpt → ext/standard/tests/pack/pack_float.phpt
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