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leechedreadcloser.go
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leechedreadcloser.go
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package ginhttplogger
import (
"io"
)
// LeechedReadCloser is a wrapper around io.ReadCloser that logs the first bytes of a Request's body
// (in our case) into a bytes buffer
type LeechedReadCloser struct {
originalReadCloser io.ReadCloser
data []byte
maxBodyLogSize int64
loggedBytesCount int64
}
// NewLeechedReadCloser creates a readCloser which reads and stores at most maxSize bytes
// from a ReadCloser and returns a clone of that same reader, data included
func NewLeechedReadCloser(source io.ReadCloser, maxSize int64) *LeechedReadCloser {
return &LeechedReadCloser{
data: make([]byte, 0, maxSize),
originalReadCloser: source,
maxBodyLogSize: maxSize,
}
}
// GetLog returns the captured log paylaod
func (l *LeechedReadCloser) GetLog() []byte {
if l.loggedBytesCount > 0 {
return l.data[:l.loggedBytesCount]
}
return []byte("[Empty or not read by server]")
}
// Read reads stores up to maxSize bytes and keeps on reading
func (l *LeechedReadCloser) Read(b []byte) (n int, err error) {
spaceLeft := l.maxBodyLogSize - l.loggedBytesCount
if spaceLeft > 0 {
// Let's read the request into our Logger (not all of it maybe), but also let's make sure that
// we'll be able to to copy all the content we read in l.data into b
n, err := l.originalReadCloser.Read(l.data[l.loggedBytesCount : l.loggedBytesCount+min(int64(len(b)), spaceLeft)])
// And copy what was read into the original slice
copy(b, l.data[l.loggedBytesCount:l.loggedBytesCount+int64(n)])
// Let's not forget to increment the pointer on the currently logged amount of bytes
l.loggedBytesCount += int64(n)
// And return what the Read() call we did on the original ReadCloser just returned, shhhhh
return n, err
}
// Our leecher is full ? Nevermind, let's just call read on the original Reader. Apart from an
// additional level in the call stack and an if statement, we have no overhead for large bodies :)
return l.originalReadCloser.Read(b)
}
// Close closes on the original ReadCloser
func (l *LeechedReadCloser) Close() (err error) {
return l.originalReadCloser.Close()
}