1 files changed, 90 insertions, 0 deletions
diff --git a/distbuild/stringbuffer.py b/distbuild/stringbuffer.py
new file mode 100644
index 00000000..3349bb87
--- /dev/null
+++ b/distbuild/stringbuffer.py
@@ -0,0 +1,90 @@
+# mainloop/stringbuffer.py -- efficient buffering of strings as a queue
+#
+# Copyright 2012 Codethink Limited
+# All rights reserved.
+
+
+class StringBuffer(object):
+
+    '''Buffer data for a file descriptor.
+    
+    The data may arrive in small pieces, and it is buffered in a way that
+    avoids excessive string catenation or splitting.
+    
+    '''
+
+    def __init__(self):
+        self.strings = []
+        self.len = 0
+        
+    def add(self, data):
+        '''Add data to buffer.'''
+        self.strings.append(data)
+        self.len += len(data)
+        
+    def remove(self, num_bytes):
+        '''Remove specified number of bytes from buffer.'''
+        while num_bytes > 0 and self.strings:
+            first = self.strings[0]
+            if len(first) <= num_bytes:
+                num_bytes -= len(first)
+                del self.strings[0]
+                self.len -= len(first)
+            else:
+                self.strings[0] = first[num_bytes:]
+                self.len -= num_bytes
+                num_bytes = 0
+
+    def peek(self):
+        '''Return contents of buffer as one string.'''
+        
+        if len(self.strings) == 0:
+            return ''
+        elif len(self.strings) == 1:
+            return self.strings[0]
+        else:
+            self.strings = [''.join(self.strings)]
+            return self.strings[0]
+
+    def read(self, max_bytes):
+        '''Return up to max_bytes from the buffer.
+        
+        Less is returned if the buffer does not contain at least max_bytes.
+        The returned data will remain in the buffer; use remove to remove
+        it.
+        
+        '''
+        
+        use = []
+        size = 0
+        for s in self.strings:
+            n = max_bytes - size
+            if len(s) <= n:
+                use.append(s)
+                size += len(s)
+            else:
+                use.append(s[:n])
+                size += n
+                break
+        return ''.join(use)
+
+    def readline(self):
+        '''Return a complete line (ends with '\n') or None.'''
+
+        for i, s in enumerate(self.strings):
+            newline = s.find('\n')
+            if newline != -1:
+                if newline+1 == len(s):
+                    use = self.strings[:i+1]
+                    del self.strings[:i+1]
+                else:
+                    pre = s[:newline+1]
+                    use = self.strings[:i] + [pre]
+                    del self.strings[:i]
+                    self.strings[0] = s[newline+1:]
+                return ''.join(use)
+        return None
+            
+    def __len__(self):
+        return self.len
+