wasm: support more vendor libraries

Adds support for:
- box2d
- cgltf
- stb image
- stb rect pack

vendor/libc/string.odin

@@ -0,0 +1,111 @@
+package odin_libc
+
+import "base:intrinsics"
+
+import "core:c"
+import "core:strings"
+import "core:mem"
+
+// NOTE: already defined by Odin.
+// void *memcpy(void *, const void *, size_t);
+// void *memset(void *, int, size_t);
+
+@(require, linkage="strong", link_name="memcmp")
+memcmp :: proc "c" (lhs: [^]byte, rhs: [^]byte, count: uint) -> i32 {
+	icount := int(count)
+	assert_contextless(icount >= 0)
+	return i32(mem.compare(lhs[:icount], rhs[:icount]))
+}
+
+@(require, linkage="strong", link_name="strlen")
+strlen :: proc "c" (str: cstring) -> c.ulong {
+	return c.ulong(len(str))
+}
+
+@(require, linkage="strong", link_name="strchr")
+strchr :: proc "c" (str: cstring, ch: i32) -> cstring {
+	bch  := u8(ch)
+	sstr := string(str)
+	if bch == 0 {
+		return cstring(raw_data(sstr)[len(sstr):])
+	}
+
+	idx := strings.index_byte(sstr, bch)
+	if idx < 0 {
+		return nil
+	}
+
+	return cstring(raw_data(sstr)[idx:])
+}
+
+@(require, linkage="strong", link_name="strrchr")
+strrchr :: proc "c" (str: cstring, ch: i32) -> cstring {
+	bch  := u8(ch)
+	sstr := string(str)
+	if bch == 0 {
+		return cstring(raw_data(sstr)[len(sstr):])
+	}
+
+	idx := strings.last_index_byte(sstr, bch)
+	if idx < 0 {
+		return nil
+	}
+
+	return cstring(raw_data(sstr)[idx:])
+}
+
+@(require, linkage="strong", link_name="strncpy")
+strncpy :: proc "c" (dst: [^]byte, src: cstring, count: uint) -> cstring {
+	icount := int(count)
+	assert_contextless(icount >= 0)
+	cnt := min(len(src), icount)
+	intrinsics.mem_copy_non_overlapping(dst, rawptr(src), cnt)
+	intrinsics.mem_zero(dst, icount-cnt)
+	return cstring(dst)
+}
+
+@(require, linkage="strong", link_name="strcpy")
+strcpy :: proc "c" (dst: [^]byte, src: cstring) -> cstring {
+	intrinsics.mem_copy_non_overlapping(dst, rawptr(src), len(src)+1)
+	return cstring(dst)
+}
+
+@(require, linkage="strong", link_name="strcspn")
+strcspn :: proc "c" (dst: cstring, src: cstring) -> uint {
+	context = g_ctx
+	sdst := string(dst)
+	idx := strings.index_any(sdst, string(src))
+	if idx == -1 {
+		return len(sdst)
+	}
+	return uint(idx)
+}
+
+@(require, linkage="strong", link_name="strncmp")
+strncmp :: proc "c" (lhs: cstring, rhs: cstring, count: uint) -> i32 {
+	icount := int(count)
+	assert_contextless(icount >= 0)
+	lhss := strings.string_from_null_terminated_ptr(([^]byte)(lhs), icount)
+	rhss := strings.string_from_null_terminated_ptr(([^]byte)(rhs), icount)
+	return i32(strings.compare(lhss, rhss))
+}
+
+@(require, linkage="strong", link_name="strcmp")
+strcmp :: proc "c" (lhs: cstring, rhs: cstring) -> i32 {
+	return i32(strings.compare(string(lhs), string(rhs)))
+}
+
+@(require, linkage="strong", link_name="strstr")
+strstr :: proc "c" (str: cstring, substr: cstring) -> cstring {
+	if substr == "" {
+		return str
+	}
+
+	idx := strings.index(string(str), string(substr))
+	if idx < 0 {
+		return nil
+	}
+
+	return cstring(([^]byte)(str)[idx:])
+}
+