From 963d1970932e9c213eaa87fbafe7c97795386d7f Mon Sep 17 00:00:00 2001 From: Ferdinand Majerech Date: Fri, 25 Jul 2014 16:52:36 +0200 Subject: [PATCH] Utilities around AppenderNoGCFixed to build error messages easily without GC. --- source/dyaml/nogcutil.d | 67 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 67 insertions(+) diff --git a/source/dyaml/nogcutil.d b/source/dyaml/nogcutil.d index 04e3376..ad715b1 100644 --- a/source/dyaml/nogcutil.d +++ b/source/dyaml/nogcutil.d @@ -63,6 +63,63 @@ body assert(!atStart, "Nothing to parse in parse()"); return v; } + + +/// Buils a message to a buffer similarly to writef/writefln, but without +/// using GC. +/// +/// C snprintf would be better, but it isn't pure. +/// formattedWrite isn't completely @nogc yet (although it isn't GC-heavy). +/// +/// The user has to ensure buffer is long enough - an assert checks that we don't run +/// out of space. Currently this can only write strings and dchars. +char[] printNoGC(S...)(char[] buffer, S args) @safe pure nothrow @nogc +{ + auto appender = appenderNoGC(buffer); + + foreach(arg; args) + { + alias A = typeof(arg); + static if(is(A == char[]) || is(A == string)) { appender.put(arg); } + else static if(is(A == dchar)) { appender.putDChar(arg); } + else static assert(false, "printNoGC does not support " ~ A.stringof); + } + + return appender.data; +} + + +/// Write a dchar to a character buffer without decoding or using the GC. +/// +/// Params: +/// +/// c = The dchar to write. Will be written as ASCII if it is in ASCII or "" +/// +/// Returns: Slice of buf containing the written dchar. +char[] writeDCharTo(dchar c, char[] buf) @safe pure nothrow @nogc +{ + const unknown = "'unknown'"; + assert(buf.length > unknown.length, "Too small buffer for writeDCharTo"); + if(c < 128) + { + buf[0] = buf[2] = '\''; + buf[1] = cast(char)c; + return buf[0 .. 3]; + } + buf[0 .. unknown.length] = unknown[] ; + return buf[0 .. unknown.length]; +} + +/// A UFCS utility function to write a dchar to an AppenderNoGCFixed using writeDCharTo. +void putDChar(ref AppenderNoGCFixed!(char[], char) appender, dchar c) + @safe pure nothrow @nogc +{ + char[16] dcharBuf; + appender.put(c.writeDCharTo(dcharBuf)); +} + /// Convenience function that returns an $(D AppenderNoGCFixed!A) using with $(D array) /// for storage. AppenderNoGCFixed!(E[]) appenderNoGC(A : E[], E)(A array) @@ -187,3 +244,13 @@ struct AppenderNoGCFixed(A : T[], T) @disable void clear(); } } + +unittest +{ + char[256] buffer; + auto appender = appenderNoGC(buffer[]); + appender.put("found unsupported escape character: "); + appender.putDChar('a'); + appender.putDChar('รก'); + assert(appender.data == "found unsupported escape character: 'a''unknown'"); +}