mirror of git://git.gnupg.org/gnupg.git
254 lines
7.0 KiB
C
254 lines
7.0 KiB
C
/* b64dec.c - Simple Base64 decoder.
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* Copyright (C) 2008, 2011 Free Software Foundation, Inc.
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* Copyright (C) 2008, 2011, 2016 g10 Code GmbH
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*
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* This file is part of GnuPG.
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* This file is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <assert.h>
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#include "i18n.h"
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#include "util.h"
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/* The reverse base-64 list used for base-64 decoding. */
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static unsigned char const asctobin[128] =
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{
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
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0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
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0x3c, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
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0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
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0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
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0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
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0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
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0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
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0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
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0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff
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};
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enum decoder_states
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{
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s_init, s_idle, s_lfseen, s_beginseen, s_waitheader, s_waitblank, s_begin,
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s_b64_0, s_b64_1, s_b64_2, s_b64_3,
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s_waitendtitle, s_waitend
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};
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/* Initialize the context for the base64 decoder. If TITLE is NULL a
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plain base64 decoding is done. If it is the empty string the
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decoder will skip everything until a "-----BEGIN " line has been
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seen, decoding ends at a "----END " line. */
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gpg_error_t
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b64dec_start (struct b64state *state, const char *title)
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{
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memset (state, 0, sizeof *state);
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if (title)
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{
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state->title = xtrystrdup (title);
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if (!state->title)
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state->lasterr = gpg_error_from_syserror ();
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else
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state->idx = s_init;
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}
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else
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state->idx = s_b64_0;
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return state->lasterr;
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}
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/* Do in-place decoding of base-64 data of LENGTH in BUFFER. Stores the
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new length of the buffer at R_NBYTES. */
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gpg_error_t
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b64dec_proc (struct b64state *state, void *buffer, size_t length,
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size_t *r_nbytes)
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{
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enum decoder_states ds = state->idx;
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unsigned char val = state->radbuf[0];
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int pos = state->quad_count;
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char *d, *s;
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if (state->lasterr)
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return state->lasterr;
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if (state->stop_seen)
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{
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*r_nbytes = 0;
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state->lasterr = gpg_error (GPG_ERR_EOF);
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xfree (state->title);
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state->title = NULL;
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return state->lasterr;
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}
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for (s=d=buffer; length && !state->stop_seen; length--, s++)
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{
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again:
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switch (ds)
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{
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case s_idle:
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if (*s == '\n')
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{
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ds = s_lfseen;
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pos = 0;
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}
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break;
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case s_init:
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ds = s_lfseen;
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case s_lfseen:
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if (*s != "-----BEGIN "[pos])
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{
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ds = s_idle;
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goto again;
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}
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else if (pos == 10)
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{
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pos = 0;
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ds = s_beginseen;
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}
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else
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pos++;
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break;
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case s_beginseen:
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if (*s != "PGP "[pos])
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ds = s_begin; /* Not a PGP armor. */
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else if (pos == 3)
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ds = s_waitheader;
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else
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pos++;
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break;
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case s_waitheader:
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if (*s == '\n')
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ds = s_waitblank;
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break;
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case s_waitblank:
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if (*s == '\n')
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ds = s_b64_0; /* blank line found. */
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else if (*s == ' ' || *s == '\r' || *s == '\t')
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; /* Ignore spaces. */
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else
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{
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/* Armor header line. Note that we don't care that our
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* FSM accepts a header prefixed with spaces. */
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ds = s_waitheader; /* Wait for next header. */
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}
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break;
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case s_begin:
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if (*s == '\n')
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ds = s_b64_0;
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break;
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case s_b64_0:
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case s_b64_1:
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case s_b64_2:
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case s_b64_3:
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{
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int c;
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if (*s == '-' && state->title)
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{
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/* Not a valid Base64 character: assume end
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header. */
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ds = s_waitend;
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}
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else if (*s == '=')
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{
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/* Pad character: stop */
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if (ds == s_b64_1)
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*d++ = val;
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ds = state->title? s_waitendtitle : s_waitend;
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}
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else if (*s == '\n' || *s == ' ' || *s == '\r' || *s == '\t')
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; /* Skip white spaces. */
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else if ( (*s & 0x80)
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|| (c = asctobin[*(unsigned char *)s]) == 255)
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{
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/* Skip invalid encodings. */
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state->invalid_encoding = 1;
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}
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else if (ds == s_b64_0)
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{
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val = c << 2;
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ds = s_b64_1;
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}
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else if (ds == s_b64_1)
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{
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val |= (c>>4)&3;
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*d++ = val;
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val = (c<<4)&0xf0;
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ds = s_b64_2;
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}
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else if (ds == s_b64_2)
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{
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val |= (c>>2)&15;
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*d++ = val;
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val = (c<<6)&0xc0;
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ds = s_b64_3;
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}
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else
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{
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val |= c&0x3f;
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*d++ = val;
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ds = s_b64_0;
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}
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}
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break;
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case s_waitendtitle:
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if (*s == '-')
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ds = s_waitend;
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break;
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case s_waitend:
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if ( *s == '\n')
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state->stop_seen = 1;
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break;
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default:
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BUG();
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}
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}
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state->idx = ds;
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state->radbuf[0] = val;
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state->quad_count = pos;
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*r_nbytes = (d -(char*) buffer);
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return 0;
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}
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/* This function needs to be called before releasing the decoder
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state. It may return an error code in case an encoding error has
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been found during decoding. */
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gpg_error_t
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b64dec_finish (struct b64state *state)
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{
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xfree (state->title);
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state->title = NULL;
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if (state->lasterr)
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return state->lasterr;
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return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0;
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}
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