gz/zlib/flate: Alias stdlib errors (#425)

Better compatibility

flate/inflate.go

@@ -9,10 +9,10 @@ package flate
 
 import (
 	"bufio"
+	"compress/flate"
 	"fmt"
 	"io"
 	"math/bits"
-	"strconv"
 	"sync"
 )
 
@@ -41,11 +41,7 @@ var fixedOnce sync.Once
 var fixedHuffmanDecoder huffmanDecoder
 
 // A CorruptInputError reports the presence of corrupt input at a given offset.
-type CorruptInputError int64
-
-func (e CorruptInputError) Error() string {
-	return "flate: corrupt input before offset " + strconv.FormatInt(int64(e), 10)
-}
+type CorruptInputError = flate.CorruptInputError
 
 // An InternalError reports an error in the flate code itself.
 type InternalError string
@@ -55,26 +51,12 @@ func (e InternalError) Error() string { return "flate: internal error: " + strin
 // A ReadError reports an error encountered while reading input.
 //
 // Deprecated: No longer returned.
-type ReadError struct {
-	Offset int64 // byte offset where error occurred
-	Err    error // error returned by underlying Read
-}
-
-func (e *ReadError) Error() string {
-	return "flate: read error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
-}
+type ReadError = flate.ReadError
 
 // A WriteError reports an error encountered while writing output.
 //
 // Deprecated: No longer returned.
-type WriteError struct {
-	Offset int64 // byte offset where error occurred
-	Err    error // error returned by underlying Write
-}
-
-func (e *WriteError) Error() string {
-	return "flate: write error at offset " + strconv.FormatInt(e.Offset, 10) + ": " + e.Err.Error()
-}
+type WriteError = flate.WriteError
 
 // Resetter resets a ReadCloser returned by NewReader or NewReaderDict to
 // to switch to a new underlying Reader. This permits reusing a ReadCloser

gzip/gunzip.go

@@ -8,8 +8,8 @@ package gzip
 
 import (
 	"bufio"
+	"compress/gzip"
 	"encoding/binary"
-	"errors"
 	"hash/crc32"
 	"io"
 	"time"
@@ -30,9 +30,9 @@ const (
 
 var (
 	// ErrChecksum is returned when reading GZIP data that has an invalid checksum.
-	ErrChecksum = errors.New("gzip: invalid checksum")
+	ErrChecksum = gzip.ErrChecksum
 	// ErrHeader is returned when reading GZIP data that has an invalid header.
-	ErrHeader = errors.New("gzip: invalid header")
+	ErrHeader = gzip.ErrHeader
 )
 
 var le = binary.LittleEndian

zlib/reader.go

@@ -25,7 +25,7 @@ package zlib
 
 import (
 	"bufio"
-	"errors"
+	"compress/zlib"
 	"hash"
 	"hash/adler32"
 	"io"
@@ -37,11 +37,11 @@ const zlibDeflate = 8
 
 var (
 	// ErrChecksum is returned when reading ZLIB data that has an invalid checksum.
-	ErrChecksum = errors.New("zlib: invalid checksum")
+	ErrChecksum = zlib.ErrChecksum
 	// ErrDictionary is returned when reading ZLIB data that has an invalid dictionary.
-	ErrDictionary = errors.New("zlib: invalid dictionary")
+	ErrDictionary = zlib.ErrDictionary
 	// ErrHeader is returned when reading ZLIB data that has an invalid header.
-	ErrHeader = errors.New("zlib: invalid header")
+	ErrHeader = zlib.ErrHeader
 )
 
 type reader struct {