107 lines
2.8 KiB
Java
107 lines
2.8 KiB
Java
/* Copyright (C) 1999 Cygnus Solutions
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package gnu.gcj.convert;
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/**
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* Convert Unicode to UTF8.
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* @author Per Bothner <bothner@cygnus.com>
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* @date Match 1999.
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*/
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public class Output_UTF8 extends UnicodeToBytes
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{
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public String getName() { return "UTF8"; }
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/** True if a surrogate pair should be emitted as a single UTF8 sequence.
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* Otherwise, a surrogate pair is treated as two separate characters.
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* Also, '\0' is emitted as {0} if true, and as {0xC0,0x80} if false. */
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public boolean standardUTF8;
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// Saves the previous char if it was a high-surrogate.
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char hi_part;
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// Value of incomplete character.
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int value;
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// Number of continuation bytes still to emit.
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int bytes_todo;
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public int write (char[] inbuffer, int inpos, int inlength)
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{
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int start_pos = inpos;
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int avail = buf.length - count;
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for (;;)
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{
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if (avail == 0 || (inlength == 0 && bytes_todo == 0))
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break;
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// The algorithm is made more complicated because we want to write
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// at least one byte in the output buffer, if there is room for
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// that byte, and at least one input character is available.
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// This makes the code more robust, since client code will
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// always "make progress", even in the complicated cases,
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// where the output buffer only has room for only *part* of a
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// multi-byte sequence, or the input char buffer only has half
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// of a surrogate pair (when standardUTF8 is set), or both.
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// Handle continuation characters we did not have room for before.
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if (bytes_todo > 0)
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{
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do
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{
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bytes_todo--;
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buf[count++] = (byte)
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(((value >> (bytes_todo * 6)) & 0x3F) | 0x80);
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avail--;
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}
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while (bytes_todo > 0 && avail > 0);
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continue;
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}
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char ch = inbuffer[inpos++];
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inlength--;
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if (ch < 128 && (ch != 0 || standardUTF8))
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{
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avail--;
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buf[count++] = (byte) ch;
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}
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else if (ch <= 0x07FF)
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{
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buf[count++] = (byte) (0xC0 | (ch >> 6));
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avail--;
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value = ch;
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bytes_todo = 1;
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}
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else if (ch >= 0xD800 && ch <= 0xDFFF && standardUTF8)
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{
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if (ch <= 0xDBFF) // High surrogates
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{
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// The first byte is (0xF0 | value>>18), where value is the
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// Unicode scalar value of the combine character - which
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// we may not know yet. But from substituting:
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// value == (hi-0xD800)*0x400+(lo-0xDC00)+0x10000,
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// hi==ch, and cancelling we get:
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buf[count++] = (byte) (0xF0 | ((ch-0xD800) >> 8));
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avail--;
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hi_part = ch;
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}
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else // Low surrogates
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{
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value = (hi_part - 0xD800) * 0x400 + (ch - 0xDC00) + 0x10000;
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bytes_todo = 3;
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}
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}
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else
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{
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buf[count++] = (byte) (0xE0 | (ch >> 12));
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value = ch;
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avail--;
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bytes_todo = 2;
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}
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}
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return inpos - start_pos;
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}
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}
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