GzipFile.readline performance improvement (~30-40%), patch #1281707
diff --git a/Lib/gzip.py b/Lib/gzip.py
index 3c1ebf2..8c7870e 100644
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -107,6 +107,7 @@
self.extrabuf = ""
self.extrasize = 0
self.filename = filename
+ self.min_readsize = 64 # Starts small, scales exponentially
elif mode[0:1] == 'w' or mode[0:1] == 'a':
self.mode = WRITE
@@ -381,32 +382,39 @@
self.read(count % 1024)
def readline(self, size=-1):
- if size < 0: size = sys.maxint
- bufs = []
- readsize = min(100, size) # Read from the file in small chunks
+ if size < 0:
+ size = sys.maxint # Line can be as long as maxint
+ readsize = self.min_readsize # Read from file in small chunks
+ else:
+ readsize = size # Only read in as much as specified
+
+ bufs = ""
+
while True:
- if size == 0:
- return "".join(bufs) # Return resulting line
+ if size == 0: return bufs # Return line (reached max len)
c = self.read(readsize)
i = c.find('\n')
- if size is not None:
- # We set i=size to break out of the loop under two
- # conditions: 1) there's no newline, and the chunk is
- # larger than size, or 2) there is a newline, but the
- # resulting line would be longer than 'size'.
- if i==-1 and len(c) > size: i=size-1
- elif size <= i: i = size -1
+ # If there is a newline, or the string is empty
if i >= 0 or c == '':
- bufs.append(c[:i+1]) # Add portion of last chunk
- self._unread(c[i+1:]) # Push back rest of chunk
- return ''.join(bufs) # Return resulting line
+ if size <= i: i = size - 1 # Another larger than size check
- # Append chunk to list, decrease 'size',
- bufs.append(c)
- size = size - len(c)
- readsize = min(size, readsize * 2)
+ self._unread(c[i+1:]) # Push back rest of chunk
+
+ return bufs + c[:i+1] # Stored line, plus new segment
+
+ # If there is no newline
+ else:
+ if len(c) > size: i = size - 1 # If lineis larger than size
+
+ bufs = bufs + c
+ size = size - len(c)
+ readsize = min(size, int(readsize * 1.1))
+
+ # Optimize future readline() calls
+ if readsize > self.min_readsize:
+ self.min_readsize = readsize
def readlines(self, sizehint=0):
# Negative numbers result in reading all the lines