[iostreams]boost\iostreams\copy.hpp line80 copy_impl

[qbowater@…]

boost\iostreams\copy.hpp line 80 - line 100

template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk,
                            std::streamsize buffer_size,
                            mpl::false_, mpl::true_ )
{   // Copy from an indirect Source to a direct Sink.
     using namespace std;
     typedef typename char_type_of<Source>::type  char_type;
     typedef pair<char_type*, char_type*>         pair_type;
     detail::basic_buffer<char_type>  buf(buffer_size);
     pair_type                        p = snk.output_sequence();
     streamsize                       total = 0;
     bool                             done  = false;
     while (!done) {
         streamsize amt;
         done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
         std::copy(buf.data(), buf.data() + amt, p.first + total);
         if (amt != -1)
             total += amt;
     }
     return total;
}

When "iostreams::read" return -1 ,amt equal -1,it will assert in std::copy because iterator last < first.

Please read ​http://article.gmane.org/gmane.comp.lib.boost.devel/161764 for detail.

[qbowater@…]

.hpp

@@ -88 +88 @@
     detail::basic_buffer<char_type>  buf(buffer_size);
     pair_type                        p = snk.output_sequence();
     streamsize                       total = 0;
-    bool                             done  = false;
-    while (!done) {
-        streamsize amt;
-        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
+    while (true) {
+        streamsize amt = iostreams::read(src, buf.data(), buffer_size);
+        if(amt == -1)
+            break;
         std::copy(buf.data(), buf.data() + amt, p.first + total);
-        if (amt != -1)
-            total += amt;
+        total += amt;
     }
     return total;
 }
@@ -109 +108 @@
     detail::basic_buffer<char_type>  buf(buffer_size);
     non_blocking_adapter<Sink>       nb(snk);
     std::streamsize                  total = 0;
-    bool                             done = false;
-    while (!done) {
-        std::streamsize amt;
-        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
-        if (amt != -1) {
-            iostreams::write(nb, buf.data(), amt);
-            total += amt;
-        }
+    while (true) {
+        std::streamsize amt = iostreams::read(src, buf.data(), buffer_size);
+        if (amt == -1)
+            break;
+        iostreams::write(nb, buf.data(), amt);
+        total += amt;
     }
     return total;
 }

--- copy.hpp	2005-05-26 01:37:30.000000000 +0800
+++ copy1.hpp	2007-07-06 15:55:17.859375000 +0800
@@ -88,13 +88,12 @@
     detail::basic_buffer<char_type>  buf(buffer_size);
     pair_type                        p = snk.output_sequence();
     streamsize                       total = 0;
-    bool                             done  = false;
-    while (!done) {
-        streamsize amt;
-        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
+    while (true) {
+        streamsize amt = iostreams::read(src, buf.data(), buffer_size);
+        if(amt == -1)
+            break;
         std::copy(buf.data(), buf.data() + amt, p.first + total);
-        if (amt != -1)
-            total += amt;
+        total += amt;
     }
     return total;
 }
@@ -109,14 +108,12 @@
     detail::basic_buffer<char_type>  buf(buffer_size);
     non_blocking_adapter<Sink>       nb(snk);
     std::streamsize                  total = 0;
-    bool                             done = false;
-    while (!done) {
-        std::streamsize amt;
-        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
-        if (amt != -1) {
-            iostreams::write(nb, buf.data(), amt);
-            total += amt;
-        }
+    while (true) {
+        std::streamsize amt = iostreams::read(src, buf.data(), buffer_size);
+        if (amt == -1)
+            break;
+        iostreams::write(nb, buf.data(), amt);
+        total += amt;
     }
     return total;
 }

[anonymous]

I think this is the same as Trac ticket # 786

[anonymous]

The proposed change at ticket #786 seems a little cleaner than the change here.

[Peter Dimov]

How did the owner become dgregor? A Trac mystery.

[Jonathan Turkanis]

Fixed in [42294] in branches/iostreams_dev, to be merged into trunk shortly. The fix is a slight modification of the suggestion in #786.