Support encodings case-insensitively

The vast majority of real world traffic uses lowercase, but some does
not, and it is technically case insensitive, so lets support it.

This also adds 'binary', yet another common content-encoding mistake
that seems to mean "there's no encoding here".

Author: pimterry

README.md

@@ -12,7 +12,7 @@ The supported codecs are:
 * Brotli
 * Zstandard
 
-The 'identity', 'amz-1.0', 'none', 'text' and 'utf-8' encodings (no-op encodings) are also supported, passed through with no en/decoding at all. Only 'identity' is standard, but the others are all in common use regardless.
+All encoding names are case-insensitive (although lowercase is generally standard). The 'identity', 'amz-1.0', 'none', 'text', 'binary' and 'utf-8' encodings (no-op encodings) are all supported as no-op encodings, passed through with no en/decoding at all. Only 'identity' is standard, but the others are all in common use regardless.
 
 Found a codec used in real-world HTTP that isn't supported? Open an issue!
 

src/index.ts

@@ -81,6 +81,7 @@ const IDENTITY_ENCODINGS = [
     // No idea where these comes from, but they definitely exist in real traffic and seem to come
     // from common confusion between content encodings and content types:
     'text',
+    'binary',
     'utf-8'
 ]
 
@@ -102,6 +103,9 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
         }, Promise.resolve(bodyBuffer as Uint8Array)) as Promise<Buffer>;
     }
 
+    if (!encoding) encoding = 'identity';
+    else encoding = encoding.toLowerCase();
+
     if (encoding === 'gzip' || encoding === 'x-gzip') {
         return gunzip(bodyBuffer);
     } else if (encoding === 'deflate' || encoding === 'x-deflate') {
@@ -118,13 +122,7 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
         return asBuffer(await brotliDecompress(bodyBuffer));
     } else if (encoding === 'zstd') {
         return asBuffer(await zstdDecompress(bodyBuffer));
-    } else if (
-        // No encoding set at all:
-        !encoding ||
-        // Explicitly unencoded:
-        IDENTITY_ENCODINGS.includes(encoding.toLowerCase())
-    ) {
-        // All of the above are different ways of saying "no encoding at all"
+    } else if (IDENTITY_ENCODINGS.includes(encoding)) {
         return asBuffer(bodyBuffer);
     }
 
@@ -154,6 +152,9 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
         }, bodyBuffer) as Buffer;
     }
 
+    if (!encoding) encoding = 'identity';
+    else encoding = encoding.toLowerCase();
+
     if (encoding === 'gzip' || encoding === 'x-gzip') {
         return zlib.gunzipSync(bodyBuffer);
     } else if (encoding === 'deflate' || encoding === 'x-deflate') {
@@ -166,16 +167,7 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
         } else {
             return zlib.inflateRawSync(bodyBuffer);
         }
-    } else if (encoding === 'amz-1.0') {
-        // Weird encoding used by some AWS requests, actually just unencoded JSON:
-        // https://docs.aws.amazon.com/en_us/AmazonCloudWatch/latest/APIReference/making-api-requests.html
-        return asBuffer(bodyBuffer);
-    } else if (
-        // No encoding set at all:
-        !encoding ||
-        // Explicitly unencoded:
-        IDENTITY_ENCODINGS.includes(encoding.toLowerCase())
-    ) {
+    } else if (IDENTITY_ENCODINGS.includes(encoding)) {
         return asBuffer(bodyBuffer);
     }
 
@@ -194,6 +186,9 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
     const bodyBuffer = asBuffer(body);
     const level = options.level ?? 4;
 
+    if (!encoding) encoding = 'identity';
+    else encoding = encoding.toLowerCase() as SUPPORTED_ENCODING;
+
     if (encoding === 'gzip' || encoding === 'x-gzip') {
         return gzip(bodyBuffer, { level });
     } else if (encoding === 'deflate' || encoding === 'x-deflate') {
@@ -206,12 +201,7 @@ export async function decodeBuffer(body: Uint8Array | ArrayBuffer, encoding: str
         } : {}));
     } else if (encoding === 'zstd') {
         return asBuffer(await zstdCompress(bodyBuffer, level));
-    } else if (
-        // No encoding set at all:
-        !encoding ||
-        // Explicitly unencoded:
-        IDENTITY_ENCODINGS.includes(encoding.toLowerCase())
-    ) {
+    } else if (IDENTITY_ENCODINGS.includes(encoding)) {
         return asBuffer(bodyBuffer);
     } else {
         throw new Error(`Unsupported encoding: ${encoding}`);

test/decode.spec.ts

@@ -95,6 +95,12 @@ describe("Decode", () => {
         const body = await decodeBuffer(content, 'br, identity, gzip, identity, zstd');
         expect(body.toString()).to.equal('First brotli, then gzip, last zstandard, now this');
     });
+
+    it('should decode bodies ignoring the code of the encoding', async () => {
+        const content = bufferToTypedArray(zlib.gzipSync('Gzip response'));
+        const body = await decodeBuffer(content, 'GZIP');
+        expect(body.toString()).to.equal('Gzip response');
+    });
 });
 
 describe("DecodeSync", () => {
@@ -153,4 +159,10 @@ describe("DecodeSync", () => {
         const body = decodeBufferSync(content, 'deflate, identity, gzip, identity');
         expect(body.toString()).to.equal('First deflate, then gzip, now this');
     });
+
+    it('should decode bodies ignoring the code of the encoding', () => {
+        const content = zlib.gzipSync('Gzip response');
+        const body = decodeBufferSync(content, 'GZIP');
+        expect(body.toString()).to.equal('Gzip response');
+    });
 });

test/encode.spec.ts

@@ -70,4 +70,9 @@ describe("Encode", () => {
             (await zstd).decompress(body)
         ).toString()).to.equal('zstd zstd body body body');
     });
+
+    it('should encode bodies ignoring the case of the encoding', async () => {
+        const body = await encodeBuffer(Buffer.from('Response to gzip'), 'gzip', { level: 1 });
+        expect(zlib.gunzipSync(body).toString()).to.equal('Response to gzip');
+    });
 });