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Add memcmp to the core. Useful in binary protocol implementations.

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This commit is contained in:
Calvin Rose 2022-10-18 11:54:07 -05:00
parent af12c3d41a
commit fd59de25c5
1 changed files with 18 additions and 0 deletions
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18
src/core/corelib.c
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@ -632,6 +632,23 @@ JANET_CORE_FN(janet_core_signal,
janet_panicf("unknown signal %v", argv[0]);
}
JANET_CORE_FN(janet_core_memcmp,
"(memcmp a b &opt len offset-a offset-b)",
"Compare memory. Takes to byte sequences `a` and `b`, and "
"return 0 if they have identical contents, a negative integer if a is less than b, "
"and a positive integer if a is greather than b. Optionally take a length and offsets "
"to compare slices of the bytes sequences.") {
janet_arity(argc, 2, 5);
JanetByteView a = janet_getbytes(argv, 0);
JanetByteView b = janet_getbytes(argv, 1);
int32_t len = janet_optnat(argv, argc, 2, a.len < b.len ? a.len : b.len);
int32_t offset_a = janet_optnat(argv, argc, 3, 0);
int32_t offset_b = janet_optnat(argv, argc, 4, 0);
if (offset_a + len > a.len) janet_panicf("invalid offset-a: %d", offset_a);
if (offset_b + len > b.len) janet_panicf("invalid offset-b: %d", offset_b);
return janet_wrap_integer(memcmp(a.bytes + offset_a, b.bytes + offset_b, (size_t) len));
}
#ifdef JANET_BOOTSTRAP
/* Utility for inline assembly */
@ -933,6 +950,7 @@ static void janet_load_libs(JanetTable *env) {
JANET_CORE_REG("nat?", janet_core_check_nat),
JANET_CORE_REG("slice", janet_core_slice),
JANET_CORE_REG("signal", janet_core_signal),
JANET_CORE_REG("memcmp", janet_core_memcmp),
JANET_CORE_REG("getproto", janet_core_getproto),
JANET_REG_END
};