Add vendor-specific version 8 UUID generation (hashing)

core/encoding/uuid/generation.odin

@@ -1,6 +1,7 @@
 package uuid
 
 import "base:runtime"
+import "core:crypto/hash"
 import "core:math/rand"
 import "core:time"
 
@@ -215,3 +216,118 @@ generate_v7 :: proc {
 	generate_v7_basic,
 	generate_v7_with_counter,
 }
+
+/*
+Generate a version 8 UUID using a specific hashing algorithm.
+
+This UUID is generated by hashing a name with a namespace.
+
+Note that all version 8 UUIDs are for experimental or vendor-specific use
+cases, per the specification. This use case in particular is for offering a
+non-legacy alternative to UUID versions 3 and 5.
+
+Inputs:
+- namespace: An `Identifier` that is used to represent the underlying namespace.
+  This can be any one of the `Namespace_*` values provided in this package.
+- name: The byte slice which will be hashed with the namespace.
+- algorithm: A hashing algorithm from `core:crypto/hash`.
+
+Returns:
+- result: The generated UUID.
+
+Example:
+	import "core:crypto/hash"
+	import "core:encoding/uuid"
+	import "core:fmt"
+
+	main :: proc() {
+		my_uuid := uuid.generate_v8_hash(uuid.Namespace_DNS, "www.odin-lang.org", .SHA256)
+		my_uuid_string := uuid.to_string(my_uuid, context.temp_allocator)
+		fmt.println(my_uuid_string)
+	}
+
+Output:
+
+	3730f688-4bff-8dce-9cbf-74a3960c5703
+
+*/
+generate_v8_hash_bytes :: proc(
+	namespace: Identifier,
+	name: []byte,
+	algorithm: hash.Algorithm,
+) -> (
+	result: Identifier,
+) {
+	// 128 bytes should be enough for the foreseeable future.
+	digest: [128]byte
+
+	assert(hash.DIGEST_SIZES[algorithm] >= 16, "Per RFC 9562, the hashing algorithm used must generate a digest of 128 bits or larger.")
+	assert(hash.DIGEST_SIZES[algorithm] < len(digest), "Digest size is too small for this algorithm. The buffer must be increased.")
+
+	hash_context: hash.Context
+	hash.init(&hash_context, algorithm)
+
+	mutable_namespace := namespace
+	hash.update(&hash_context, mutable_namespace[:])
+	hash.update(&hash_context, name[:])
+	hash.final(&hash_context, digest[:])
+
+	runtime.mem_copy_non_overlapping(&result, &digest, 16)
+
+	result[VERSION_BYTE_INDEX] &= 0x0F
+	result[VERSION_BYTE_INDEX] |= 0x80
+
+	result[VARIANT_BYTE_INDEX] &= 0x3F
+	result[VARIANT_BYTE_INDEX] |= 0x80
+
+	return
+}
+
+/*
+Generate a version 8 UUID using a specific hashing algorithm.
+
+This UUID is generated by hashing a name with a namespace.
+
+Note that all version 8 UUIDs are for experimental or vendor-specific use
+cases, per the specification. This use case in particular is for offering a
+non-legacy alternative to UUID versions 3 and 5.
+
+Inputs:
+- namespace: An `Identifier` that is used to represent the underlying namespace.
+  This can be any one of the `Namespace_*` values provided in this package.
+- name: The string which will be hashed with the namespace.
+- algorithm: A hashing algorithm from `core:crypto/hash`.
+
+Returns:
+- result: The generated UUID.
+
+Example:
+	import "core:crypto/hash"
+	import "core:encoding/uuid"
+	import "core:fmt"
+
+	main :: proc() {
+		my_uuid := uuid.generate_v8_hash(uuid.Namespace_DNS, "www.odin-lang.org", .SHA256)
+		my_uuid_string := uuid.to_string(my_uuid, context.temp_allocator)
+		fmt.println(my_uuid_string)
+	}
+
+Output:
+
+	3730f688-4bff-8dce-9cbf-74a3960c5703
+
+*/
+generate_v8_hash_string :: proc(
+	namespace: Identifier,
+	name: string,
+	algorithm: hash.Algorithm,
+) -> (
+	result: Identifier,
+) {
+	return generate_v8_hash_bytes(namespace, transmute([]byte)name, algorithm)
+}
+
+generate_v8_hash :: proc {
+	generate_v8_hash_bytes,
+	generate_v8_hash_string,
+}