121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
|
-
-
-
+
+
+
+
-
+
-
+
|
// and decompresses data according to the predictor algorithm
func Decompressor(reader io.Reader) io.Reader {
var ctx context
ctx.input = make([]byte, 0, 8)
return decompressor(func(output []byte) (int, error) {
var (
err error
flags byte
rc, available, predicted int
err error
flags byte
rc, available, predicted, total int
)
// Sanity check for space to read into
if len(output) == 0 {
return 0, nil
}
// Check whether we have leftover data in the buffer
if len(ctx.input) > 0 {
rc = copy(output, ctx.input)
// Check whether we still have leftover data in the buffer :)
if rc < len(ctx.input) {
ctx.input = ctx.input[:copy(ctx.input, ctx.input[rc:])]
}
return rc, nil
}
// Read the next prediction header
readHeader:
rc, err = reader.Read(ctx.input[:1])
// Fail on error unless it is EOF
if err != nil && err != io.EOF {
return 0, err
return total, err
} else if rc == 0 {
return 0, err
return total, err
}
// Extend the buffer, copy the prediction header
// and calculate the number of subsequent bytes to read
ctx.input = ctx.input[:8]
flags = ctx.input[0]
predicted = int(bits.Hamming(flags))
|
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
|
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
|
+
+
-
-
-
+
+
+
+
+
+
+
+
|
// Update the hash
ctx.hash = (ctx.hash << 4) ^ uint16(ctx.input[i])
}
// rc now contains the precise amount of populated data
ctx.input = ctx.input[:rc]
available = copy(output, ctx.input)
total += available
// Check for remaining bytes that dont fit in the output buffer
if available < rc {
ctx.input = ctx.input[:copy(ctx.input, ctx.input[available:])]
} else {
// Clear the buffer
ctx.input = ctx.input[:0]
}
return available, err
output = output[available:]
if len(output) > 0 && err == nil {
goto readHeader
}
}
return total, err
})
}
|