func()

in decode.go [121:234]

• 99 lines of code
• 26 McCabe index (conditional complexity)

func (r *Reader) fill() error {
	for r.i >= r.j {
		if !r.readFull(r.buf[:4], true) {
			return r.err
		}
		chunkType := r.buf[0]
		if !r.readHeader {
			if chunkType != chunkTypeStreamIdentifier {
				r.err = ErrCorrupt
				return r.err
			}
			r.readHeader = true
		}
		chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
		if chunkLen > len(r.buf) {
			r.err = ErrUnsupported
			return r.err
		}

		// The chunk types are specified at
		// https://github.com/google/snappy/blob/master/framing_format.txt
		switch chunkType {
		case chunkTypeCompressedData:
			// Section 4.2. Compressed data (chunk type 0x00).
			if chunkLen < checksumSize {
				r.err = ErrCorrupt
				return r.err
			}
			buf := r.buf[:chunkLen]
			if !r.readFull(buf, false) {
				return r.err
			}
			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
			buf = buf[checksumSize:]

			n, err := DecodedLen(buf)
			if err != nil {
				r.err = err
				return r.err
			}
			if n > len(r.decoded) {
				r.err = ErrCorrupt
				return r.err
			}
			if _, err := Decode(r.decoded, buf); err != nil {
				r.err = err
				return r.err
			}
			if crc(r.decoded[:n]) != checksum {
				r.err = ErrCorrupt
				return r.err
			}
			r.i, r.j = 0, n
			continue

		case chunkTypeUncompressedData:
			// Section 4.3. Uncompressed data (chunk type 0x01).
			if chunkLen < checksumSize {
				r.err = ErrCorrupt
				return r.err
			}
			buf := r.buf[:checksumSize]
			if !r.readFull(buf, false) {
				return r.err
			}
			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
			// Read directly into r.decoded instead of via r.buf.
			n := chunkLen - checksumSize
			if n > len(r.decoded) {
				r.err = ErrCorrupt
				return r.err
			}
			if !r.readFull(r.decoded[:n], false) {
				return r.err
			}
			if crc(r.decoded[:n]) != checksum {
				r.err = ErrCorrupt
				return r.err
			}
			r.i, r.j = 0, n
			continue

		case chunkTypeStreamIdentifier:
			// Section 4.1. Stream identifier (chunk type 0xff).
			if chunkLen != len(magicBody) {
				r.err = ErrCorrupt
				return r.err
			}
			if !r.readFull(r.buf[:len(magicBody)], false) {
				return r.err
			}
			for i := 0; i < len(magicBody); i++ {
				if r.buf[i] != magicBody[i] {
					r.err = ErrCorrupt
					return r.err
				}
			}
			continue
		}

		if chunkType <= 0x7f {
			// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
			r.err = ErrUnsupported
			return r.err
		}
		// Section 4.4 Padding (chunk type 0xfe).
		// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
		if !r.readFull(r.buf[:chunkLen], false) {
			return r.err
		}
	}

	return nil
}