Clean up the hex handling

3 files changed, 20 insertions, 38 deletions

diff --git a/internal/jsonparse/hex.go b/internal/jsonparse/hex.go
deleted file mode 100644
index 3ed5f01..0000000
--- a/internal/jsonparse/hex.go
+++ /dev/null
@@ -1,20 +0,0 @@
-// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
-//
-// SPDX-License-Identifier: GPL-2.0-or-later
-
-package jsonparse
-
-const Hex = "0123456789abcdef"
-
-func HexToInt(c rune) (byte, bool) {
-	switch {
-	case '0' <= c && c <= '9':
-		return byte(c) - '0', true
-	case 'a' <= c && c <= 'f':
-		return byte(c) - 'a' + 10, true
-	case 'A' <= c && c <= 'F':
-		return byte(c) - 'A' + 10, true
-	default:
-		return 0, false
-	}
-}
diff --git a/internal/jsonparse/parse.go b/internal/jsonparse/parse.go
index 73584d9..2f5c1ab 100644
--- a/internal/jsonparse/parse.go
+++ b/internal/jsonparse/parse.go
@@ -14,6 +14,12 @@ import (
 
 var ErrParserExceededMaxDepth = errors.New("exceeded max depth")
 
+func isHex(c rune) bool {
+	return ('0' <= c && c <= '9') ||
+		('a' <= c && c <= 'f') ||
+		('A' <= c && c <= 'F')
+}
+
 // RuneType is the classification of a rune when parsing JSON input.
 // A Parser, rather than grouping runes into tokens and classifying
 // tokens, classifies runes directly.
@@ -667,30 +673,26 @@ func (par *Parser) HandleRune(c rune) (RuneType, error) {
 			return RuneTypeError, fmt.Errorf("string backslash sequence: unexpected character: %q", c)
 		}
 	case RuneTypeStringEscU:
-		if _, ok := HexToInt(c); ok {
-			return par.replaceState(RuneTypeStringEscUA), nil
-		} else {
+		if !isHex(c) {
 			return RuneTypeError, fmt.Errorf("string unicode sequence: unexpected character: %q", c)
 		}
+		return par.replaceState(RuneTypeStringEscUA), nil
 	case RuneTypeStringEscUA:
-		if _, ok := HexToInt(c); ok {
-			return par.replaceState(RuneTypeStringEscUB), nil
-		} else {
+		if !isHex(c) {
 			return RuneTypeError, fmt.Errorf("string unicode sequence: unexpected character: %q", c)
 		}
+		return par.replaceState(RuneTypeStringEscUB), nil
 	case RuneTypeStringEscUB:
-		if _, ok := HexToInt(c); ok {
-			return par.replaceState(RuneTypeStringEscUC), nil
-		} else {
+		if !isHex(c) {
 			return RuneTypeError, fmt.Errorf("string unicode sequence: unexpected character: %q", c)
 		}
+		return par.replaceState(RuneTypeStringEscUC), nil
 	case RuneTypeStringEscUC:
-		if _, ok := HexToInt(c); ok {
-			par.replaceState(RuneTypeStringBeg)
-			return RuneTypeStringEscUD, nil
-		} else {
+		if !isHex(c) {
 			return RuneTypeError, fmt.Errorf("string unicode sequence: unexpected character: %q", c)
 		}
+		par.replaceState(RuneTypeStringBeg)
+		return RuneTypeStringEscUD, nil
 	// number //////////////////////////////////////////////////////////////////////////////////
 	//
 	// Here's a flattened drawing of the syntax diagram from www.json.org :
diff --git a/internal/jsonstring/encode_string.go b/internal/jsonstring/encode_string.go
index f29dc3f..a7670c6 100644
--- a/internal/jsonstring/encode_string.go
+++ b/internal/jsonstring/encode_string.go
@@ -10,7 +10,6 @@ import (
 	"unicode/utf8"
 
 	"git.lukeshu.com/go/lowmemjson/internal/fastio"
-	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 // BackslashEscapeMode is describe in the main lowmemjson package
@@ -27,13 +26,14 @@ const (
 type BackslashEscaper = func(rune, BackslashEscapeMode) BackslashEscapeMode
 
 func writeStringUnicodeEscape(w io.Writer, c rune) (int, error) {
+	const alphabet = "0123456789abcdef"
 	buf := [6]byte{
 		'\\',
 		'u',
-		jsonparse.Hex[(c>>12)&0xf],
-		jsonparse.Hex[(c>>8)&0xf],
-		jsonparse.Hex[(c>>4)&0xf],
-		jsonparse.Hex[(c>>0)&0xf],
+		alphabet[(c>>12)&0xf],
+		alphabet[(c>>8)&0xf],
+		alphabet[(c>>4)&0xf],
+		alphabet[(c>>0)&0xf],
 	}
 	return w.Write(buf[:])
 }