text: // Copyright 2014 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package http2
  
  import (
  	"errors"
  	"fmt"
  )
  
  // An ErrCode is an unsigned 32-bit error code as defined in the HTTP/2 spec.
  type ErrCode uint32
  
  const (
  	ErrCodeNo                 ErrCode = 0x0
  	ErrCodeProtocol           ErrCode = 0x1
  	ErrCodeInternal           ErrCode = 0x2
  	ErrCodeFlowControl        ErrCode = 0x3
  	ErrCodeSettingsTimeout    ErrCode = 0x4
  	ErrCodeStreamClosed       ErrCode = 0x5
  	ErrCodeFrameSize          ErrCode = 0x6
  	ErrCodeRefusedStream      ErrCode = 0x7
  	ErrCodeCancel             ErrCode = 0x8
  	ErrCodeCompression        ErrCode = 0x9
  	ErrCodeConnect            ErrCode = 0xa
  	ErrCodeEnhanceYourCalm    ErrCode = 0xb
  	ErrCodeInadequateSecurity ErrCode = 0xc
  	ErrCodeHTTP11Required     ErrCode = 0xd
  )
  
  var errCodeName = map[ErrCode]string{
  	ErrCodeNo:                 "NO_ERROR",
  	ErrCodeProtocol:           "PROTOCOL_ERROR",
  	ErrCodeInternal:           "INTERNAL_ERROR",
  	ErrCodeFlowControl:        "FLOW_CONTROL_ERROR",
  	ErrCodeSettingsTimeout:    "SETTINGS_TIMEOUT",
  	ErrCodeStreamClosed:       "STREAM_CLOSED",
  	ErrCodeFrameSize:          "FRAME_SIZE_ERROR",
  	ErrCodeRefusedStream:      "REFUSED_STREAM",
  	ErrCodeCancel:             "CANCEL",
  	ErrCodeCompression:        "COMPRESSION_ERROR",
  	ErrCodeConnect:            "CONNECT_ERROR",
  	ErrCodeEnhanceYourCalm:    "ENHANCE_YOUR_CALM",
  	ErrCodeInadequateSecurity: "INADEQUATE_SECURITY",
  	ErrCodeHTTP11Required:     "HTTP_1_1_REQUIRED",
  }
  
  func (e ErrCode) String() string {
  	if s, ok := errCodeName[e]; ok {
  		return s
  	}
  	return fmt.Sprintf("unknown error code 0x%x", uint32(e))
  }
  
  // ConnectionError is an error that results in the termination of the
  // entire connection.
  type ConnectionError ErrCode
  
  func (e ConnectionError) Error() string { return fmt.Sprintf("connection error: %s", ErrCode(e)) }
  
  // StreamError is an error that only affects one stream within an
  // HTTP/2 connection.
  type StreamError struct {
  	StreamID uint32
  	Code     ErrCode
  	Cause    error // optional additional detail
  }
  
  func streamError(id uint32, code ErrCode) StreamError {
  	return StreamError{StreamID: id, Code: code}
  }
  
  func (e StreamError) Error() string {
  	if e.Cause != nil {
  		return fmt.Sprintf("stream error: stream ID %d; %v; %v", e.StreamID, e.Code, e.Cause)
  	}
  	return fmt.Sprintf("stream error: stream ID %d; %v", e.StreamID, e.Code)
  }
  
  // 6.9.1 The Flow Control Window
  // "If a sender receives a WINDOW_UPDATE that causes a flow control
  // window to exceed this maximum it MUST terminate either the stream
  // or the connection, as appropriate. For streams, [...]; for the
  // connection, a GOAWAY frame with a FLOW_CONTROL_ERROR code."
  type goAwayFlowError struct{}
  
  func (goAwayFlowError) Error() string { return "connection exceeded flow control window size" }
  
  // connErrorReason wraps a ConnectionError with an informative error about why it occurs.
  
  // Errors of this type are only returned by the frame parser functions
  // and converted into ConnectionError(ErrCodeProtocol).
  type connError struct {
  	Code   ErrCode
  	Reason string
  }
  
  func (e connError) Error() string {
  	return fmt.Sprintf("http2: connection error: %v: %v", e.Code, e.Reason)
  }
  
  type pseudoHeaderError string
  
  func (e pseudoHeaderError) Error() string {
  	return fmt.Sprintf("invalid pseudo-header %q", string(e))
  }
  
  type duplicatePseudoHeaderError string
  
  func (e duplicatePseudoHeaderError) Error() string {
  	return fmt.Sprintf("duplicate pseudo-header %q", string(e))
  }
  
  type headerFieldNameError string
  
  func (e headerFieldNameError) Error() string {
  	return fmt.Sprintf("invalid header field name %q", string(e))
  }
  
  type headerFieldValueError string
  
  func (e headerFieldValueError) Error() string {
  	return fmt.Sprintf("invalid header field value %q", string(e))
  }
  
  var (
  	errMixPseudoHeaderTypes = errors.New("mix of request and response pseudo headers")
  	errPseudoAfterRegular   = errors.New("pseudo header field after regular")
  )
  