repo_description: The Official Golang driver for MongoDB
repo_topics: database driver go golang golang-library mongodb
code: // Copyright (C) MongoDB, Inc. 2025-present.
  //
  // 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
  
  // Package binaryutil provides utility functions for working with binary data.
  package binaryutil
  
  import (
  	"bytes"
  	"encoding/binary"
  )
  
  // Append32 appends a uint32 or int32 value to dst in little-endian byte order.
  // Byte shifting is done directly to prevent overflow security errors, in
  // compliance with gosec G115.
  //
  // See: https://cs.opensource.google/go/go/+/refs/tags/go1.19:src/encoding/binary/binary.go;l=92
  func Append32[T ~uint32 | ~int32](dst []byte, v T) []byte {
  	return append(dst,
  		byte(v),
  		byte(v>>8),
  		byte(v>>16),
  		byte(v>>24),
  	)
  }
  
  // Append64 appends a uint64 or int64 value to dst in little-endian byte order.
  // Byte shifting is done directly to prevent overflow security errors, in
  // compliance with gosec G115.
  //
  // See: https://cs.opensource.google/go/go/+/refs/tags/go1.19:src/encoding/binary/binary.go;l=119
  func Append64[T ~uint64 | ~int64](dst []byte, v T) []byte {
  	return append(dst,
  		byte(v),
  		byte(v>>8),
  		byte(v>>16),
  		byte(v>>24),
  		byte(v>>32),
  		byte(v>>40),
  		byte(v>>48),
  		byte(v>>56),
  	)
  }
  
  // ReadU32 reads a uint32 from src in little-endian byte order. ReadU32 and
  // ReadI32 are separate functions to avoid unsafe casting between unsigned and
  // signed integers.
  func ReadU32(src []byte) (uint32, []byte, bool) {
  	if len(src) < 4 {
  		return 0, src, false
  	}
  
  	return binary.LittleEndian.Uint32(src), src[4:], true
  }
  
  // ReadI32 reads an int32 from src in little-endian byte order.
  // Byte shifting is done directly to prevent overflow security errors, in
  // compliance with gosec G115. ReadU32 and ReadI32 are separate functions to
  // avoid unsafe casting between unsigned and signed integers.
  //
  // See: https://cs.opensource.google/go/go/+/refs/tags/go1.19:src/encoding/binary/binary.go;l=79
  func ReadI32(src []byte) (int32, []byte, bool) {
  	if len(src) < 4 {
  		return 0, src, false
  	}
  
  	_ = src[3] // bounds check hint to compiler
  
  	value := int32(src[0]) |
  		int32(src[1])<<8 |
  		int32(src[2])<<16 |
  		int32(src[3])<<24
  
  	return value, src[4:], true
  }
  
  // ReadU64 reads a uint64 from src in little-endian byte order. ReadU64 and
  // ReadI64 are separate functions to avoid unsafe casting between unsigned and
  // signed integers.
  func ReadU64(src []byte) (uint64, []byte, bool) {
  	if len(src) < 8 {
  		return 0, src, false
  	}
  
  	return binary.LittleEndian.Uint64(src), src[8:], true
  }
  
  // ReadI64 reads an int64 from src in little-endian byte order.
  // Byte shifting is done directly to prevent overflow security errors, in
  // compliance with gosec G115. ReadU64 and ReadI64 are separate functions to
  // avoid unsafe casting between unsigned and signed integers.
  //
  // See: https://cs.opensource.google/go/go/+/refs/tags/go1.19:src/encoding/binary/binary.go;l=101
  func ReadI64(src []byte) (int64, []byte, bool) {
  	if len(src) < 8 {
  		return 0, src, false
  	}
  
  	_ = src[7] // bounds check hint to compiler
  
  	value := int64(src[0]) |
  		int64(src[1])<<8 |
  		int64(src[2])<<16 |
  		int64(src[3])<<24 |
  		int64(src[4])<<32 |
  		int64(src[5])<<40 |
  		int64(src[6])<<48 |
  		int64(src[7])<<56
  
  	return value, src[8:], true
  }
  
  // ReadCStringBytes reads a null-terminated C string from src as a byte slice.
  // This is the base implementation used by ReadCString to ensure a single source
  // of truth for C string parsing logic.
  func ReadCStringBytes(src []byte) ([]byte, []byte, bool) {
  	idx := bytes.IndexByte(src, 0x00)
  	if idx < 0 {
  		return nil, src, false
  	}
  	return src[:idx], src[idx+1:], true
  }
  
  // ReadCString reads a null-terminated C string from src as a string.
  // It delegates to ReadCStringBytes to maintain a single source of truth for
  // C string parsing logic.
  func ReadCString(src []byte) (string, []byte, bool) {
  	cstr, rem, ok := ReadCStringBytes(src)
  	if !ok {
  		return "", src, false
  	}
  	return string(cstr), rem, true
  }
  