From: Daira Hopwood <daira@jacaranda.org>
Date: Wed, 1 May 2013 02:41:41 +0000 (+0100)
Subject: Cleanup: improve error reporting for DataTooLargeError
X-Git-Url: https://git.rkrishnan.org/simplejson/components/%22doc.html/(%5B%5E?a=commitdiff_plain;h=0336046e3cf7b19cdd604b65fcbe57ba7ca878a6;p=tahoe-lafs%2Ftahoe-lafs.git

Cleanup: improve error reporting for DataTooLargeError
(and fix an off-by-one error in MutableDiskShare._write_share_data).

Signed-off-by: Daira Hopwood <david-sarah@jacaranda.org>
---

diff --git a/src/allmydata/storage/backends/cloud/immutable.py b/src/allmydata/storage/backends/cloud/immutable.py
index 45e60bd1..41f0dbb3 100644
--- a/src/allmydata/storage/backends/cloud/immutable.py
+++ b/src/allmydata/storage/backends/cloud/immutable.py
@@ -75,7 +75,7 @@ class ImmutableCloudShareForWriting(CloudShareBase, ImmutableCloudShareMixin):
         seekpos = self.DATA_OFFSET + offset
         precondition(seekpos >= self._total_size, offset=offset, seekpos=seekpos, total_size=self._total_size)
         if offset + len(data) > self._allocated_data_length:
-            raise DataTooLargeError(self._allocated_data_length, offset, len(data))
+            raise DataTooLargeError(self._shnum, self._allocated_data_length, offset, len(data))
 
         self._set_size(self._total_size + len(data))
         return self._store_or_buffer( (seekpos, data, 0) )
diff --git a/src/allmydata/storage/backends/cloud/mutable.py b/src/allmydata/storage/backends/cloud/mutable.py
index 7ee1af62..2314f52f 100644
--- a/src/allmydata/storage/backends/cloud/mutable.py
+++ b/src/allmydata/storage/backends/cloud/mutable.py
@@ -219,7 +219,7 @@ class MutableCloudShare(CloudShareBase, CloudShareReaderMixin):
             length = len(data)
             precondition(offset >= 0, offset=offset)
             if offset + length > self.MAX_SIZE:
-                raise DataTooLargeError()
+                raise DataTooLargeError(self._shnum, self.MAX_SIZE, offset, length)
 
             if new_length is not None and new_length < offset + length:
                 length = max(0, new_length - offset)
diff --git a/src/allmydata/storage/backends/disk/immutable.py b/src/allmydata/storage/backends/disk/immutable.py
index 056863c5..bd8af51c 100644
--- a/src/allmydata/storage/backends/disk/immutable.py
+++ b/src/allmydata/storage/backends/disk/immutable.py
@@ -190,7 +190,8 @@ class ImmutableDiskShare(object):
         length = len(data)
         precondition(offset >= 0, offset)
         if self._allocated_data_length is not None and offset+length > self._allocated_data_length:
-            raise DataTooLargeError(self._allocated_data_length, offset, length)
+            raise DataTooLargeError(self._shnum, self._allocated_data_length, offset, length)
+
         f = open(self._home, 'rb+')
         try:
             real_offset = self.DATA_OFFSET + offset
diff --git a/src/allmydata/storage/backends/disk/mutable.py b/src/allmydata/storage/backends/disk/mutable.py
index 253df514..c86abaa4 100644
--- a/src/allmydata/storage/backends/disk/mutable.py
+++ b/src/allmydata/storage/backends/disk/mutable.py
@@ -174,17 +174,13 @@ class MutableDiskShare(object):
     def _write_share_data(self, f, offset, data):
         length = len(data)
         precondition(offset >= 0, offset=offset)
-        precondition(offset + length < self.MAX_SIZE, offset=offset, length=length)
+        if offset + length > self.MAX_SIZE:
+            raise DataTooLargeError(self._shnum, self.MAX_SIZE, offset, length)
 
         data_length = self._read_data_length(f)
 
         if offset+length >= data_length:
-            # They are expanding their data size.
-
-            if offset+length > self.MAX_SIZE:
-                raise DataTooLargeError()
-
-            # Their data now fits in the current container. We must write
+            # They are expanding their data size. We must write
             # their new data and modify the recorded data size.
 
             # Fill any newly exposed empty space with 0's.
@@ -263,7 +259,7 @@ class MutableDiskShare(object):
         for (offset, data) in datav:
             precondition(offset >= 0, offset=offset)
             if offset + len(data) > self.MAX_SIZE:
-                raise DataTooLargeError()
+                raise DataTooLargeError(self._shnum, self.MAX_SIZE, offset, len(data))
 
         f = open(self._home, 'rb+')
         try:
diff --git a/src/allmydata/storage/common.py b/src/allmydata/storage/common.py
index 5417da30..959aa83b 100644
--- a/src/allmydata/storage/common.py
+++ b/src/allmydata/storage/common.py
@@ -11,7 +11,15 @@ PREFIX = re.compile("^[%s]{2}$" % (base32.z_base_32_alphabet,))
 
 
 class DataTooLargeError(Exception):
-    pass
+    def __init__(self, shnum, allocated_data_length, offset, length):
+        self.shnum = shnum
+        self.allocated_data_length = allocated_data_length
+        self.offset = offset
+        self.length = length
+
+    def __str__(self):
+        return ("attempted write to shnum %d of %d bytes at offset %d exceeds allocated data length of %d bytes"
+                % (self.__class__.__name__, self.shnum, self.length, self.offset, self.allocated_data_length))
 
 
 class CorruptStoredShareError(Exception):