no changes, just added some explanatory comments for wxCSConv members

[wxWidgets.git] / src / common / strconv.cpp

diff --git a/src/common/strconv.cpp b/src/common/strconv.cpp
index 54ac2c84894ead9adbf148c4d6aab4e94838d248..91958d6e61895a547cb788d71f63c4bd190f2e1e 100644 (file)
--- a/src/common/strconv.cpp
+++ b/src/common/strconv.cpp
@@ -160,11 +160,15 @@ wxMBConv::ToWChar(wchar_t *dst, size_t dstLen,
                   const char *src, size_t srcLen) const
 {
     // although new conversion classes are supposed to implement this function
-    // directly, the existins ones only implement the old MB2WC() and so, to
+    // directly, the existing ones only implement the old MB2WC() and so, to
     // avoid to have to rewrite all conversion classes at once, we provide a
     // default (but not efficient) implementation of this one in terms of the
     // old function by copying the input to ensure that it's NUL-terminated and
     // then using MB2WC() to convert it
+    //
+    // moreover, some conversion classes simply can't implement ToWChar()
+    // directly, the primary example is wxConvLibc: mbstowcs() only handles
+    // NUL-terminated strings
 
     // the number of chars [which would be] written to dst [if it were not NULL]
     size_t dstWritten = 0;
@@ -205,6 +209,21 @@ wxMBConv::ToWChar(wchar_t *dst, size_t dstLen,
         srcEnd = NULL;
     }
 
+    // the idea of this code is straightforward: it converts a NUL-terminated
+    // chunk of the string during each iteration and updates the output buffer
+    // with the result
+    //
+    // all the complication come from the fact that this function, for
+    // historical reasons, must behave in 2 subtly different ways when it's
+    // called with a fixed number of characters and when it's called for the
+    // entire NUL-terminated string: in the former case (srcEnd == NULL) we
+    // must count all characters we convert, NUL or not; but in the latter we
+    // do not count the trailing NUL -- but still count all the NULs inside the
+    // string
+    //
+    // so for the (simple) former case we just always count the trailing NUL,
+    // but for the latter we need to wait until we see if there is going to be
+    // another loop iteration and only count it then
     for ( ;; )
     {
         // try to convert the current chunk
@@ -257,9 +276,19 @@ wxMBConv::ToWChar(wchar_t *dst, size_t dstLen,
 
         // note that ">=" (and not just "==") is needed here as the terminator
         // we skipped just above could be inside or just after the buffer
-        // delimited by inEnd
+        // delimited by srcEnd
         if ( src >= srcEnd )
             break;
+
+        // if we got here then this wasn't the last chunk in this string and
+        // hence we must count an extra char for L'\0' even when converting a
+        // fixed number of characters
+        if ( srcEnd )
+        {
+            dstWritten++;
+            if ( dst )
+                dst++;
+        }
     }
 
     return dstWritten;
@@ -536,14 +565,14 @@ static const unsigned char utf7unb64[] =
     0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
     0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
     0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff 
+    0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
 };
 
 size_t wxMBConvUTF7::ToWChar(wchar_t *dst, size_t dstLen,
                              const char *src, size_t srcLen) const
 {
     DecoderState stateOrig,
-         *statePtr;
+                *statePtr;
     if ( srcLen == wxNO_LEN )
     {
         // convert the entire string, up to and including the trailing NUL
@@ -580,7 +609,20 @@ size_t wxMBConvUTF7::ToWChar(wchar_t *dst, size_t dstLen,
             const unsigned char dc = utf7unb64[cc];
             if ( dc == 0xff )
             {
-                // end of encoded part
+                // end of encoded part, check that nothing was left: there can
+                // be up to 4 bits of 0 padding but nothing else (we also need
+                // to check isLSB as we count bits modulo 8 while a valid UTF-7
+                // encoded sequence must contain an integral number of UTF-16
+                // characters)
+                if ( state.isLSB || state.bit > 4 ||
+                        (state.accum & ((1 << state.bit) - 1)) )
+                {
+                    if ( !len )
+                        state = stateOrig;
+
+                    return wxCONV_FAILED;
+                }
+
                 state.ToDirect();
 
                 // re-parse this character normally below unless it's '-' which
@@ -624,9 +666,6 @@ size_t wxMBConvUTF7::ToWChar(wchar_t *dst, size_t dstLen,
             // start of an encoded segment?
             if ( cc == '+' )
             {
-                if ( src == srcEnd )
-                    return wxCONV_FAILED; // can't have '+' at the end
-
                 if ( *src == '-' )
                 {
                     // just the encoded plus sign, don't switch to shifted mode
@@ -635,7 +674,15 @@ size_t wxMBConvUTF7::ToWChar(wchar_t *dst, size_t dstLen,
                     len++;
                     src++;
                 }
-                else
+                else if ( utf7unb64[(unsigned)*src] == 0xff )
+                {
+                    // empty encoded chunks are not allowed
+                    if ( !len )
+                        state = stateOrig;
+
+                    return wxCONV_FAILED;
+                }
+                else // base-64 encoded chunk follows
                 {
                     state.ToShifted();
                 }