Initial commit

Author: itpey

README.md

@@ -1 +1,67 @@
-# pathcodec
+# pathcodec
+
+![Go Version](https://img.shields.io/badge/Go-1.24%2B-blue)
+![Go Reference](https://pkg.go.dev/badge/github.com/itpey/pathcodec.svg)
+![ReportCard](https://goreportcard.com/badge/github.com/itpey/pathcodec)
+![Coverage](https://coveralls.io/repos/github/itpey/pathcodec/badge.svg?branch=main)
+![License](https://img.shields.io/github/license/itpey/pathcodec)
+
+A lightweight Go package for compressing and decompressing
+[Telegram vector thumbnails](https://core.telegram.org/api/files#vector-thumbnails).
+
+## Installation
+
+```sh
+go get -u github.com/itpey/pathcodec
+```
+
+## Usage
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/itpey/pathcodec"
+)
+
+func main() {
+	compressed, err := pathcodec.Compress("M257,455c-56,0-109-25-146-65-143-156,31-397,224-318,201,83,136,386-78,383z")
+	if err != nil {
+		fmt.Println("Compression error:", err)
+		return
+	}
+	fmt.Println("Compressed:", compressed)
+
+	decompressed, err := pathcodec.Decompress(compressed)
+	if err != nil {
+		fmt.Println("Decompression error:", err)
+		return
+	}
+	fmt.Println("Decompressed:", decompressed)
+}
+```
+
+## API
+
+### `func Compress(path string) ([]byte, error)`
+
+Compresses a path string into a compact byte format. The input must start with 'M' and end with 'z'.
+
+### `func Decompress(encoded []byte) (string, error)`
+
+Decompresses a byte slice back into a path string.
+
+## Feedback and Contributions
+
+If you encounter any issues or have suggestions for improvement, please [open an issue](https://github.com/itpey/pathcodec/issues) on GitHub.
+
+We welcome contributions! Fork the repository, make your changes, and submit a pull request.
+
+## License
+
+pathcodec is open-source software released under the MIT License. You can find a copy of the license in the [LICENSE](https://github.com/itpey/pathcodec/blob/main/LICENSE) file.
+
+## Author
+
+pathcodec was created by [itpey](https://github.com/itpey)

go.mod

@@ -0,0 +1,3 @@
+module github.com/itpey/pathcodec
+
+go 1.24.1

go.sum

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+github.com/klauspost/cpuid/v2 v2.2.10 h1:tBs3QSyvjDyFTq3uoc/9xFpCuOsJQFNPiAhYdw2skhE=
+github.com/klauspost/cpuid/v2 v2.2.10/go.mod h1:hqwkgyIinND0mEev00jJYCxPNVRVXFQeu1XKlok6oO0=
+golang.org/x/sys v0.30.0 h1:QjkSwP/36a20jFYWkSue1YwXzLmsV5Gfq7Eiy72C1uc=
+golang.org/x/sys v0.30.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

pathcodec.go

@@ -0,0 +1,72 @@
+package pathcodec
+
+import (
+	"errors"
+	"fmt"
+)
+
+var charToIndex = [256]byte{}
+var indexToChar = "AACAAAAHAAALMAAAQASTAVAAAZaacaaaahaaalmaaaqastava.az0123456789-,"
+
+func init() {
+	for i := range charToIndex {
+		charToIndex[i] = 255
+	}
+	for i, c := range indexToChar {
+		charToIndex[c] = byte(i)
+	}
+}
+
+func Compress(path string) ([]byte, error) {
+	if len(path) < 2 || path[0] != 'M' || path[len(path)-1] != 'z' {
+		return nil, errors.New("invalid input: must start with 'M' and end with 'z'")
+	}
+
+	length := len(path) - 2 // Exclude 'M' and 'z'
+	encoded := make([]byte, length)
+
+	for i := 1; i < len(path)-1; i++ {
+		char := path[i]
+		if char == ',' {
+			encoded[i-1] = 128
+		} else if char == '-' {
+			encoded[i-1] = 64
+		} else if char >= '0' && char <= '9' {
+			encoded[i-1] = char - '0'
+		} else if charToIndex[char] == 255 {
+			return nil, fmt.Errorf("invalid character '%c' in input", char)
+		} else {
+			encoded[i-1] = charToIndex[char] + 192
+		}
+	}
+	return encoded, nil
+}
+
+func Decompress(encoded []byte) (string, error) {
+	if len(encoded) == 0 {
+		return "", errors.New("invalid input: encoded data cannot be empty")
+	}
+	length := len(encoded) + 2
+	path := make([]byte, length)
+	path[0] = 'M'
+	path[length-1] = 'z'
+
+	for i, num := range encoded {
+		num = num & 0xff
+		if num >= 192 {
+			if int(num-192) >= len(indexToChar) {
+				return "", fmt.Errorf("invalid encoded byte: %d", num)
+			}
+			path[i+1] = indexToChar[num-192]
+		} else if num >= 128 {
+			path[i+1] = ','
+		} else if num >= 64 {
+			path[i+1] = '-'
+		} else if num <= 9 {
+			path[i+1] = '0' + num
+		} else {
+			return "", fmt.Errorf("invalid encoded byte: %d", num)
+		}
+	}
+	return string(path), nil
+}

pathcodec_test.go

@@ -0,0 +1,62 @@
+package pathcodec
+
+import (
+	"testing"
+)
+
+func TestComprkessDecompress(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+		wantErr  bool
+	}{
+		{"Valid path", "M257,455c-56,0-109-25-146-65-143-156,31-397,224-318,201,83,136,386-78,383z", "M257,455c-56,0-109-25-146-65-143-156,31-397,224-318,201,83,136,386-78,383z", false},
+		{"Valid path", "M255,491h-182l-1-2-2-2,0-231,0-231,2-1,2-2h182,182l1,2,2,2v230,231l-2,2-2,2h-182z", "M255,491h-182l-1-2-2-2,0-231,0-231,2-1,2-2h182,182l1,2,2,2v230,231l-2,2-2,2h-182z", false},
+		{"Valid path", "M256,330h-28l-2-2-2-2,1-2,0-2-13-119-14-119,0-4,0-4,3-3,2-2h56,55l2,2,2,2v2l1,2-14,123-14,123-2,3-3,2h-27z", "M256,330h-28l-2-2-2-2,1-2,0-2-13-119-14-119,0-4,0-4,3-3,2-2h56,55l2,2,2,2v2l1,2-14,123-14,123-2,3-3,2h-27z", false},
+		{"Valid path", "M258,458h-211l-1-1-2-2,1-9,1-9,0-62,0-63,1-119,1-118,1-2,2-2,0-6,0-6,2-1,2-1h206,206l2,1,2,1v6,7h2l2,1,1,3v3l1,126,1,125v52,52,10l1,10-2,2-2,2h-210z", "M258,458h-211l-1-1-2-2,1-9,1-9,0-62,0-63,1-119,1-118,1-2,2-2,0-6,0-6,2-1,2-1h206,206l2,1,2,1v6,7h2l2,1,1,3v3l1,126,1,125v52,52,10l1,10-2,2-2,2h-210z", false},
+		{"Valid path", "M134,465h-3l1-1,0-2,1-2,0-2,59-90,58-91v1h-69l-69,1,1-2,1-1,0-2,0-2,107-105,108-105,8-8,8-8,2,1h2l1,2v2l-39,81-40,82h71l71,1v2,2l-2,2-1,2-134,123-133,122h-3z", "M134,465h-3l1-1,0-2,1-2,0-2,59-90,58-91v1h-69l-69,1,1-2,1-1,0-2,0-2,107-105,108-105,8-8,8-8,2,1h2l1,2v2l-39,81-40,82h71l71,1v2,2l-2,2-1,2-134,123-133,122h-3z", false},
+		{"Valid path", "M256,478c-108,0-111,14-112-98,0-26-6-173,0-184,2-3-10-32-2-40,5-5-3-84,9-102,6-10,18-17,30-18,30-3,136-7,161,2,8,3,15,8,20,15,16,20,7,89,7,115,0,79,0,163,0,245,0,15,4,34-6,47-21,30-75,18-106,18z", "M256,478c-108,0-111,14-112-98,0-26-6-173,0-184,2-3-10-32-2-40,5-5-3-84,9-102,6-10,18-17,30-18,30-3,136-7,161,2,8,3,15,8,20,15,16,20,7,89,7,115,0,79,0,163,0,245,0,15,4,34-6,47-21,30-75,18-106,18z", false},
+		{"Valid path with letters", "MASTAVAz", "MASTAVAz", false},
+		{"Invalid start character", "X1-3,5-7,9z", "", true},
+		{"Invalid end character", "M1-3,5-7,9y", "", true},
+		{"Invalid character in path", "M1-3,5-7,9$z", "", true},
+		{"Empty path", "", "", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			encoded, err := Compress(tt.input)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("compress() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if err != nil {
+				return
+			}
+
+			decoded, err := Decompress(encoded)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("decompress() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if decoded != tt.expected {
+				t.Errorf("decompress() = %v, expected %v", decoded, tt.expected)
+			}
+		})
+	}
+}
+
+func BenchmarkCompress(b *testing.B) {
+	path := "M257,455c-56,0-109-25-146-65-143-156,31-397,224-318,201,83,136,386-78,383z"
+	for i := 0; i < b.N; i++ {
+		_, _ = Compress(path)
+	}
+}
+
+func BenchmarkDecompress(b *testing.B) {
+	encoded := []byte{2, 5, 7, 128, 4, 5, 5, 220, 64, 5, 6, 128, 0, 64, 1, 0, 9, 64, 2, 5, 64, 1, 4, 6, 64, 6, 5, 64, 1, 4, 3, 64, 1, 5, 6, 128, 3, 1, 64, 3, 9, 7, 128, 2, 2, 4, 64, 3, 1, 8, 128, 2, 0, 1, 128, 8, 3, 128, 1, 3, 6, 128, 3, 8, 6, 64, 7, 8, 128, 3, 8, 3}
+	for i := 0; i < b.N; i++ {
+		_, _ = Decompress(encoded)
+	}
+}