dyaml/source/dyaml/unused.d

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5.1 KiB
D

// Copyright Ferdinand Majerech 2014.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Code that is currently unused but may be useful for future D:YAML releases
module dyaml.unused;
import std.utf;
import tinyendian;
// Decode an UTF-8/16/32 buffer to UTF-32 (for UTF-32 this does nothing).
//
// Params:
//
// input = The UTF-8/16/32 buffer to decode.
// encoding = Encoding of input.
//
// Returns:
//
// A struct with the following members:
//
// $(D string errorMessage) In case of a decoding error, the error message is stored
// here. If there was no error, errorMessage is NULL. Always
// check this first before using the other members.
// $(D dchar[] decoded) A GC-allocated buffer with decoded UTF-32 characters.
auto decodeUTF(ubyte[] input, UTFEncoding encoding) @safe pure nothrow
{
// Documented in function ddoc.
struct Result
{
string errorMessage;
dchar[] decoded;
}
Result result;
// Decode input_ if it's encoded as UTF-8 or UTF-16.
//
// Params:
//
// buffer = The input buffer to decode.
// result = A Result struct to put decoded result and any error messages to.
//
// On error, result.errorMessage will be set.
static void decode(C)(C[] input, ref Result result) @safe pure nothrow
{
// End of part of input that contains complete characters that can be decoded.
const size_t end = endOfLastUTFSequence(input);
// If end is 0, there are no full chars.
// This can happen at the end of file if there is an incomplete UTF sequence.
if(end < input.length)
{
result.errorMessage = "Invalid UTF character at the end of input";
return;
}
const srclength = input.length;
try for(size_t srcpos = 0; srcpos < srclength;)
{
const c = input[srcpos];
if(c < 0x80)
{
result.decoded ~= c;
++srcpos;
}
else
{
result.decoded ~= std.utf.decode(input, srcpos);
}
}
catch(UTFException e)
{
result.errorMessage = e.msg;
return;
}
catch(Exception e)
{
assert(false, "Unexpected exception in decode(): " ~ e.msg);
}
}
final switch(encoding)
{
case UTFEncoding.UTF_8: decode(cast(char[])input, result); break;
case UTFEncoding.UTF_16:
assert(input.length % 2 == 0, "UTF-16 buffer size must be even");
decode(cast(wchar[])input, result);
break;
case UTFEncoding.UTF_32:
assert(input.length % 4 == 0,
"UTF-32 buffer size must be a multiple of 4");
// No need to decode anything
result.decoded = cast(dchar[])input;
break;
}
if(result.errorMessage !is null) { return result; }
return result;
}
// Determine the end of last UTF-8 or UTF-16 sequence in a raw buffer.
size_t endOfLastUTFSequence(C)(const C[] buffer)
@safe pure nothrow @nogc
{
static if(is(C == char))
{
for(long end = buffer.length - 1; end >= 0; --end)
{
const stride = utf8Stride[buffer[cast(size_t)end]];
if(stride != 0xFF)
{
// If stride goes beyond end of the buffer, return end.
// Otherwise the last sequence ends at buffer.length, so we can
// return that. (Unless there is an invalid code unit, which is
// caught at decoding)
return (stride > buffer.length - end) ? cast(size_t)end : buffer.length;
}
}
return 0;
}
else static if(is(C == wchar))
{
// TODO this is O(N), which is slow. Find out if we can somehow go
// from the end backwards with UTF-16.
size_t end = 0;
while(end < buffer.length)
{
const s = stride(buffer, end);
if(s + end > buffer.length) { break; }
end += s;
}
return end;
}
}
// UTF-8 codepoint strides (0xFF are codepoints that can't start a sequence).
immutable ubyte[256] utf8Stride =
[
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
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,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
4,4,4,4,4,4,4,4,5,5,5,5,6,6,0xFF,0xFF,
];