hack: documentataion

Signed-off-by: Vicent Marti <vmg@strn.cat>

go/hack/compat.go

@@ -1,17 +1,34 @@
 //go:build !gc || wasm
 
+/*
+Copyright 2021 The Vitess Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package hack
 
+// String returns b as a string. This compat function allocates memory.
 func String(b []byte) (s string) {
 	return string(b)
 }
 
+// StringBytes returns as a []byte. This compat function allocates memory.
 func StringBytes(s string) []byte {
 	return []byte(s)
 }
 
-func DisableProtoBufRandomness() {}
-
+// RuntimeMemhash is a slow hash function for bytes, implemented for compatibility.
 func RuntimeMemhash(b []byte, hash uint64) uint64 {
 	for i := 0; i < len(b); i++ {
 		hash *= 1099511628211
@@ -20,6 +37,7 @@ func RuntimeMemhash(b []byte, hash uint64) uint64 {
 	return hash
 }
 
+// RuntimeStrhash is a slow hash function for bytes, implemented for compatibility.
 func RuntimeStrhash(str string, hash uint64) uint64 {
 	for i := 0; i < len(str); i++ {
 		hash *= 1099511628211
@@ -28,9 +46,12 @@ func RuntimeStrhash(str string, hash uint64) uint64 {
 	return hash
 }
 
+// ParseFloatPrefix exposes the internal strconv method from the standard library
+//
 //go:linkname ParseFloatPrefix strconv.parseFloatPrefix
 func ParseFloatPrefix(s string, bitSize int) (float64, int, error)
 
+// RuntimeAllocSize is a no-op when Vitess is not compiled with GC
 func RuntimeAllocSize(size int64) int64 {
 	return size
 }

go/hack/detrand.go

@@ -1,5 +1,3 @@
-//go:build gc && !wasm
-
 /*
 Copyright 2021 The Vitess Authors.