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Use deferred error handling for pgx.MessageReader

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This commit is contained in:
Jack Christensen 2013-07-20 08:36:33 -05:00
parent fd287527fe
commit ce2d53c4fb
1 changed files with 81 additions and 19 deletions
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100
message_reader.go
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@ -3,51 +3,113 @@ package pgx
import ( import (
"bytes" "bytes"
"encoding/binary" "encoding/binary"
"fmt"
) )
// MessageReader is a helper that reads values from a PostgreSQL message. // MessageReader is a helper that reads values from a PostgreSQL message.
// To avoid verbose error handling it internally records errors and no-ops
// any calls that occur after an error. At the end of a sequence of reads
// the Err field should be checked to see if any errors occurred.
type MessageReader struct { type MessageReader struct {
buf *bytes.Buffer buf *bytes.Buffer
Err error
} }
func newMessageReader(buf *bytes.Buffer) *MessageReader { func newMessageReader(buf *bytes.Buffer) *MessageReader {
return &MessageReader{buf: buf} return &MessageReader{buf: buf}
} }
func (r *MessageReader) ReadByte() byte { func (r *MessageReader) ReadByte() (b byte) {
b, err := r.buf.ReadByte() if r.Err != nil {
if err != nil { return
panic("Unable to read byte")
} }
return b
b, r.Err = r.buf.ReadByte()
return
} }
func (r *MessageReader) ReadInt16() int16 { func (r *MessageReader) ReadInt16() (n int16) {
return int16(binary.BigEndian.Uint16(r.buf.Next(2))) if r.Err != nil {
return
}
size := 2
b := r.buf.Next(size)
if len(b) != size {
r.Err = fmt.Errorf("Unable to read %d bytes, only read %d", size, len(b))
}
return int16(binary.BigEndian.Uint16(b))
} }
func (r *MessageReader) ReadInt32() int32 { func (r *MessageReader) ReadInt32() (n int32) {
return int32(binary.BigEndian.Uint32(r.buf.Next(4))) if r.Err != nil {
return
}
size := 4
b := r.buf.Next(size)
if len(b) != size {
r.Err = fmt.Errorf("Unable to read %d bytes, only read %d", size, len(b))
}
return int32(binary.BigEndian.Uint32(b))
} }
func (r *MessageReader) ReadInt64() int64 { func (r *MessageReader) ReadInt64() (n int64) {
return int64(binary.BigEndian.Uint64(r.buf.Next(8))) if r.Err != nil {
return
}
size := 8
b := r.buf.Next(size)
if len(b) != size {
r.Err = fmt.Errorf("Unable to read %d bytes, only read %d", size, len(b))
}
return int64(binary.BigEndian.Uint64(b))
} }
func (r *MessageReader) ReadOid() Oid { func (r *MessageReader) ReadOid() (oid Oid) {
return Oid(binary.BigEndian.Uint32(r.buf.Next(4))) if r.Err != nil {
return
}
size := 4
b := r.buf.Next(size)
if len(b) != size {
r.Err = fmt.Errorf("Unable to read %d bytes, only read %d", size, len(b))
}
return Oid(binary.BigEndian.Uint32(b))
} }
// ReadString reads a null terminated string // ReadString reads a null terminated string
func (r *MessageReader) ReadString() string { func (r *MessageReader) ReadString() (s string) {
b, err := r.buf.ReadBytes(0) if r.Err != nil {
if err != nil { return
panic("Unable to read string")
} }
var b []byte
b, r.Err = r.buf.ReadBytes(0)
if r.Err != nil {
return
}
return string(b[:len(b)-1]) return string(b[:len(b)-1])
} }
// ReadByteString reads count bytes and return as string // ReadByteString reads count bytes and return as string
func (r *MessageReader) ReadByteString(count int32) string { func (r *MessageReader) ReadByteString(count int32) (s string) {
return string(r.buf.Next(int(count))) if r.Err != nil {
return
}
size := int(count)
b := r.buf.Next(size)
if len(b) != size {
r.Err = fmt.Errorf("Unable to read %d bytes, only read %d", size, len(b))
}
return string(b)
} }