http://d.puremagic.com/issues/show_bug.cgi?id=9725

           Summary: std.string.format does wasteful UTF decoding
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: performance
          Severity: normal
          Priority: P3
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: thecybershadow@gmail.com


--- Comment #0 from Vladimir Panteleev <thecybershadow@gmail.com> 2013-03-15 06:14:17 EET ---
import std.string; void main() { format("\xFF"); }

This program throws, indicating that the "format" function performs UTF-8 decoding.

This is a pointless waste of cycles. All format specifiers are in the lower-ASCII range, and both the input and output are UTF-8. Should the format specifier syntax require reading exactly one Unicode character, it should do so when required, rather than reading the entire string one dchar at a time, then encoding the results back into an UTF-8 string.

It is worth noting that writefln does not have the same issue.

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--- Comment #1 from Vladimir Panteleev <thecybershadow@gmail.com> 2013-03-15 06:20:54 EET ---
Actually, it looks like a bug in a static if in Appender.put(). Looking into
it.

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--- Comment #2 from Vladimir Panteleev <thecybershadow@gmail.com> 2013-03-15 06:35:24 EET ---
Looks like the fix to issue 5663 wasn't complete, because
const(immutable(char)) is immutable(char), not const(char).

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Vladimir Panteleev <thecybershadow@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #3 from Vladimir Panteleev <thecybershadow@gmail.com> 2013-03-15 06:41:28 EET ---
https://github.com/D-Programming-Language/phobos/pull/1209

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--- Comment #4 from github-bugzilla@puremagic.com 2013-03-17 02:40:19 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/0b1f86119a1bb0776bd15bd843286cf1c920d264
std.array: Fix inefficient appending of const(char)[] (Issue 9725)

https://github.com/D-Programming-Language/phobos/commit/f4ddfec8d6645231a6a9b6869c25e0f1ba4f5a3f Merge pull request #1209 from CyberShadow/fix9725

std.array: Fix inefficient appending of const(char)[] (Issue 9725)

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #5 from Kenji Hara <k.hara.pg@gmail.com> 2013-07-13 06:48:25 PDT ---
Fixed in 2.063.

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