diff options
Diffstat (limited to 'lib/jython/Lib/StringIO.py')
| -rw-r--r-- | lib/jython/Lib/StringIO.py | 208 |
1 files changed, 208 insertions, 0 deletions
diff --git a/lib/jython/Lib/StringIO.py b/lib/jython/Lib/StringIO.py new file mode 100644 index 000000000..89796f2f1 --- /dev/null +++ b/lib/jython/Lib/StringIO.py @@ -0,0 +1,208 @@ +"""File-like objects that read from or write to a string buffer.
+
+This implements (nearly) all stdio methods.
+
+f = StringIO() # ready for writing
+f = StringIO(buf) # ready for reading
+f.close() # explicitly release resources held
+flag = f.isatty() # always false
+pos = f.tell() # get current position
+f.seek(pos) # set current position
+f.seek(pos, mode) # mode 0: absolute; 1: relative; 2: relative to EOF
+buf = f.read() # read until EOF
+buf = f.read(n) # read up to n bytes
+buf = f.readline() # read until end of line ('\n') or EOF
+list = f.readlines()# list of f.readline() results until EOF
+f.truncate([size]) # truncate file at to at most size (default: current pos)
+f.write(buf) # write at current position
+f.writelines(list) # for line in list: f.write(line)
+f.getvalue() # return whole file's contents as a string
+
+Notes:
+- Using a real file is often faster (but less convenient).
+- There's also a much faster implementation in C, called cStringIO, but
+ it's not subclassable.
+- fileno() is left unimplemented so that code which uses it triggers
+ an exception early.
+- Seeking far beyond EOF and then writing will insert real null
+ bytes that occupy space in the buffer.
+- There's a simple test set (see end of this file).
+"""
+
+try:
+ from errno import EINVAL
+except ImportError:
+ EINVAL = 22
+
+__all__ = ["StringIO"]
+
+class StringIO:
+ def __init__(self, buf = ''):
+ self.buf = buf
+ self.len = len(buf)
+ self.buflist = []
+ self.pos = 0
+ self.closed = 0
+ self.softspace = 0
+
+ def close(self):
+ if not self.closed:
+ self.closed = 1
+ del self.buf, self.pos
+
+ def isatty(self):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ return 0
+
+ def seek(self, pos, mode = 0):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ if self.buflist:
+ self.buf += ''.join(self.buflist)
+ self.buflist = []
+ if mode == 1:
+ pos += self.pos
+ elif mode == 2:
+ pos += self.len
+ self.pos = max(0, pos)
+
+ def tell(self):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ return self.pos
+
+ def read(self, n = -1):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ if self.buflist:
+ self.buf += ''.join(self.buflist)
+ self.buflist = []
+ if n < 0:
+ newpos = self.len
+ else:
+ newpos = min(self.pos+n, self.len)
+ r = self.buf[self.pos:newpos]
+ self.pos = newpos
+ return r
+
+ def readline(self, length=None):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ if self.buflist:
+ self.buf += ''.join(self.buflist)
+ self.buflist = []
+ i = self.buf.find('\n', self.pos)
+ if i < 0:
+ newpos = self.len
+ else:
+ newpos = i+1
+ if length is not None:
+ if self.pos + length < newpos:
+ newpos = self.pos + length
+ r = self.buf[self.pos:newpos]
+ self.pos = newpos
+ return r
+
+ def readlines(self, sizehint = 0):
+ total = 0
+ lines = []
+ line = self.readline()
+ while line:
+ lines.append(line)
+ total += len(line)
+ if 0 < sizehint <= total:
+ break
+ line = self.readline()
+ return lines
+
+ def truncate(self, size=None):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ if size is None:
+ size = self.pos
+ elif size < 0:
+ raise IOError(EINVAL, "Negative size not allowed")
+ elif size < self.pos:
+ self.pos = size
+ self.buf = self.getvalue()[:size]
+
+ def write(self, s):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+ if not s: return
+ if self.pos > self.len:
+ self.buflist.append('\0'*(self.pos - self.len))
+ self.len = self.pos
+ newpos = self.pos + len(s)
+ if self.pos < self.len:
+ if self.buflist:
+ self.buf += ''.join(self.buflist)
+ self.buflist = []
+ self.buflist = [self.buf[:self.pos], s, self.buf[newpos:]]
+ self.buf = ''
+ if newpos > self.len:
+ self.len = newpos
+ else:
+ self.buflist.append(s)
+ self.len = newpos
+ self.pos = newpos
+
+ def writelines(self, list):
+ self.write(''.join(list))
+
+ def flush(self):
+ if self.closed:
+ raise ValueError, "I/O operation on closed file"
+
+ def getvalue(self):
+ if self.buflist:
+ self.buf += ''.join(self.buflist)
+ self.buflist = []
+ return self.buf
+
+
+# A little test suite
+
+def test():
+ import sys
+ if sys.argv[1:]:
+ file = sys.argv[1]
+ else:
+ file = '/etc/passwd'
+ lines = open(file, 'r').readlines()
+ text = open(file, 'r').read()
+ f = StringIO()
+ for line in lines[:-2]:
+ f.write(line)
+ f.writelines(lines[-2:])
+ if f.getvalue() != text:
+ raise RuntimeError, 'write failed'
+ length = f.tell()
+ print 'File length =', length
+ f.seek(len(lines[0]))
+ f.write(lines[1])
+ f.seek(0)
+ print 'First line =', `f.readline()`
+ here = f.tell()
+ line = f.readline()
+ print 'Second line =', `line`
+ f.seek(-len(line), 1)
+ line2 = f.read(len(line))
+ if line != line2:
+ raise RuntimeError, 'bad result after seek back'
+ f.seek(len(line2), 1)
+ list = f.readlines()
+ line = list[-1]
+ f.seek(f.tell() - len(line))
+ line2 = f.read()
+ if line != line2:
+ raise RuntimeError, 'bad result after seek back from EOF'
+ print 'Read', len(list), 'more lines'
+ print 'File length =', f.tell()
+ if f.tell() != length:
+ raise RuntimeError, 'bad length'
+ f.close()
+
+if __name__ == '__main__':
+ test()
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