for len(src) >= gcmBlockSize { aes.EncryptBlockInternal(b, mask[:], counter[:]) gcmInc32(counter) subtle.XORBytes(out, src, mask[:]) out = out[gcmBlockSize:] src = src[gcmBlockSize:] } if len(src) > 0 { aes.EncryptBlockInternal(b, mask[:], counter[:]) gcmInc32(counter) subtle.XORBytes(out, src, mask[:]) } } // gcmInc32 treats the final four bytes of counterBlock as a big-endian value // and increments it. func gcmInc32(counterBlock *[gcmBlockSize]byte) { ctr := counterBlock[len(counterBlock)-4:] ...