[sextante] Log file is now read backwards and limited to a fixed numb…

…er of lines

python/plugins/sextante/core/SextanteLog.py

@@ -87,9 +87,13 @@ def getLogEntries():
         warnings=[]
         info=[]
         #lines = codecs.open(SextanteLog.logFilename(), encoding='utf-8')
-        lines = open(SextanteLog.logFilename())
-        line = lines.readline()
-        while line != "":
+        #=======================================================================
+        # lines = open(SextanteLog.logFilename())
+        # line = lines.readline()
+        # while line != "":
+        #=======================================================================
+        lines = tail(SextanteLog.logFilename())
+        for line in lines:
             line = line.strip("\n").strip()
             tokens = line.split("|")
             text=""
@@ -103,8 +107,8 @@ def getLogEntries():
                 warnings.append(LogEntry(tokens[1], text))
             elif line.startswith(SextanteLog.LOG_INFO):
                 info.append(LogEntry(tokens[1], text))
-            line = lines.readline()
-        lines.close()
+            #line = lines.readline()
+        #lines.close()
         entries[SextanteLog.LOG_ERROR] = errors
         entries[SextanteLog.LOG_ALGORITHM] = algorithms
         entries[SextanteLog.LOG_INFO] = info
@@ -133,3 +137,139 @@ class LogEntry():
     def __init__(self, date, text):
         self.date = date
         self.text = text
+
+import re
+import time
+
+
+
+#===============================================================================
+
+#this code has been take from pytailer
+# http://code.google.com/p/pytailer/
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy of this software 
+# and associated documentation files (the "Software"), to deal in the Software without restriction, 
+# including without limitation the rights to use, copy, modify, merge, publish, distribute, 
+# sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is 
+# furnished to do so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included in all 
+# copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING 
+# BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, 
+# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#===============================================================================
+
+class Tailer(object):
+    """\
+    Implements tailing and heading functionality like GNU tail and head
+    commands.
+    """
+    line_terminators = ('\r\n', '\n', '\r')
+
+    def __init__(self, filename, read_size=1024, end=False):
+        self.read_size = read_size
+        self.file = open(filename)
+        self.start_pos = self.file.tell()
+        if end:
+            self.seek_end()
+
+    def splitlines(self, data):
+        return re.split('|'.join(self.line_terminators), data)
+
+    def seek_end(self):
+        self.seek(0, 2)
+
+    def seek(self, pos, whence=0):
+        self.file.seek(pos, whence)
+
+    def read(self, read_size=None):
+        if read_size:
+            read_str = self.file.read(read_size)
+        else:
+            read_str = self.file.read()
+
+        return len(read_str), read_str
+
+    def seek_line(self):
+        """\
+        Searches backwards from the current file position for a line terminator
+        and seeks to the charachter after it.
+        """
+        pos = end_pos = self.file.tell()
+
+        read_size = self.read_size
+        if pos > read_size:
+            pos -= read_size
+        else:
+            pos = 0
+            read_size = end_pos
+
+        self.seek(pos)
+
+        bytes_read, read_str = self.read(read_size)
+
+        if bytes_read and read_str[-1] in self.line_terminators:
+            # The last charachter is a line terminator, don't count this one
+            bytes_read -= 1
+
+            if read_str[-2:] == '\r\n' and '\r\n' in self.line_terminators:
+                # found crlf
+                bytes_read -= 1
+
+        while bytes_read > 0:          
+            # Scan backward, counting the newlines in this bufferfull
+            i = bytes_read - 1
+            while i >= 0:
+                if read_str[i] in self.line_terminators:
+                    self.seek(pos + i + 1)
+                    return self.file.tell()
+                i -= 1
+
+            if pos == 0 or pos - self.read_size < 0:
+                # Not enought lines in the buffer, send the whole file
+                self.seek(0)
+                return None
+
+            pos -= self.read_size
+            self.seek(pos)
+
+            bytes_read, read_str = self.read(self.read_size)
+
+        return None
+
+    def tail(self, lines=10):
+        """\
+        Return the last lines of the file.
+        """
+        self.seek_end()
+        end_pos = self.file.tell()
+
+        for i in xrange(lines):
+            if not self.seek_line():
+                break
+
+        data = self.file.read(end_pos - self.file.tell() - 1)
+        if data:
+            return self.splitlines(data)
+        else:
+            return []
+
+
+
+    def __iter__(self):
+        return self.follow()
+
+    def close(self):
+        self.file.close()
+
+def tail(file, lines=200):
+    return Tailer(file).tail(lines)
+
+
+
+