nssb64e.c

来自「支持SSL v2/v3, TLS, PKCS #5, PKCS #7, PKCS」· C语言 代码 · 共 763 行 · 第 1/2 页

/*
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is the Netscape security libraries.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1994-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s):
 * 
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
 * instead of those above.  If you wish to allow use of your 
 * version of this file only under the terms of the GPL and not to
 * allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by
 * the GPL.  If you do not delete the provisions above, a recipient
 * may use your version of this file under either the MPL or the
 * GPL.
 */

/*
 * Base64 encoding (binary to ascii).
 *
 * $Id: nssb64e.c,v 1.1 2000/04/06 00:39:49 repka%netscape.com Exp $
 */

#include "nssb64.h"
#include "nspr.h"
#include "secitem.h"
#include "secerr.h"

/*
 * XXX See the big comment at the top of nssb64d.c about moving the
 * bulk of this code over into NSPR (the PL part).  It all applies
 * here but I didn't want to duplicate it, to avoid divergence problems.
 */ 

/*
 **************************************************************
 * XXX Beginning of base64 encoding code to be moved into NSPR.
 */


struct PLBase64EncodeStateStr {
    unsigned chunks;
    unsigned saved;
    unsigned char buf[3];
};

/*
 * This typedef would belong in the NSPR header file (i.e. plbase64.h).
 */
typedef struct PLBase64EncoderStr PLBase64Encoder;

/*
 * The following implementation of base64 encoding was based on code
 * found in libmime (specifically, in mimeenc.c).  It has been adapted to
 * use PR types and naming as well as to provide other necessary semantics
 * (like buffer-in/buffer-out in addition to "streaming" without undue
 * performance hit of extra copying if you made the buffer versions
 * use the output_fn).  It also incorporates some aspects of the current
 * NSPR base64 encoding code.  As such, you may find similarities to
 * both of those implementations.  I tried to use names that reflected
 * the original code when possible.  For this reason you may find some
 * inconsistencies -- libmime used lots of "in" and "out" whereas the
 * NSPR version uses "src" and "dest"; sometimes I changed one to the other
 * and sometimes I left them when I thought the subroutines were at least
 * self-consistent.
 */

PR_BEGIN_EXTERN_C

/*
 * Opaque object used by the encoder to store state.
 */
struct PLBase64EncoderStr {
    /*
     * The one or two bytes pending.  (We need 3 to create a "token",
     * and hold the leftovers here.  in_buffer_count is *only* ever
     * 0, 1, or 2.
     */
    unsigned char in_buffer[2];
    int in_buffer_count;

    /*
     * If the caller wants linebreaks added, line_length specifies
     * where they come out.  It must be a multiple of 4; if the caller
     * provides one that isn't, we round it down to the nearest
     * multiple of 4.
     *
     * The value of current_column counts how many characters have been
     * added since the last linebreaks (or since the beginning, on the
     * first line).  It is also always a multiple of 4; it is unused when
     * line_length is 0.
     */ 
    PRUint32 line_length;
    PRUint32 current_column;

    /*
     * Where to write the encoded data (used when streaming, not when
     * doing all in-memory (buffer) operations).
     *
     * Note that this definition is chosen to be compatible with PR_Write.
     */
    PRInt32 (*output_fn) (void *output_arg, const char *buf, PRInt32 size);
    void *output_arg;

    /*
     * Where the encoded output goes -- either temporarily (in the streaming
     * case, staged here before it goes to the output function) or what will
     * be the entire buffered result for users of the buffer version.
     */
    char *output_buffer;
    PRUint32 output_buflen;	/* the total length of allocated buffer */
    PRUint32 output_length;	/* the length that is currently populated */
};

PR_END_EXTERN_C


/*
 * Table to convert a binary value to its corresponding ascii "code".
 */
static unsigned char base64_valuetocode[64] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

#define B64_PAD	'='
#define B64_CR	'\r'
#define B64_LF	'\n'

static PRStatus
pl_base64_encode_buffer (PLBase64Encoder *data, const unsigned char *in,
			 PRUint32 size)
{
    const unsigned char *end = in + size;
    char *out = data->output_buffer + data->output_length;
    int i = data->in_buffer_count;
    PRUint32 n = 0;
    int off;
    PRUint32 output_threshold;

    /* If this input buffer is too small, wait until next time. */
    if (size < (3 - i)) {
	data->in_buffer[i++] = in[0];
	if (size > 1)
	    data->in_buffer[i++] = in[1];
	PR_ASSERT(i < 3);
	data->in_buffer_count = i;
	return PR_SUCCESS;
    }

    /* If there are bytes that were put back last time, take them now. */
    if (i > 0) {
	n = data->in_buffer[0];
	if (i > 1)
	    n = (n << 8) | data->in_buffer[1];
	data->in_buffer_count = 0;
    }

    /* If our total is not a multiple of three, put one or two bytes back. */
    off = (size + i) % 3;
    if (off > 0) {
	size -= off;
	data->in_buffer[0] = in[size];
	if (off > 1)
	    data->in_buffer[1] = in[size + 1];
	data->in_buffer_count = off;
	end -= off;
    }

    output_threshold = data->output_buflen - 3;

    /*
     * Populate the output buffer with base64 data, one line (or buffer)
     * at a time.
     */
    while (in < end) {
	int j, k;

	while (i < 3) {
	    n = (n << 8) | *in++;
	    i++;
	}
	i = 0;

	if (data->line_length > 0) {
	    if (data->current_column >= data->line_length) {
		data->current_column = 0;
		*out++ = B64_CR;
		*out++ = B64_LF;
		data->output_length += 2;
	    }
	    data->current_column += 4;	/* the bytes we are about to add */
	}

	for (j = 18; j >= 0; j -= 6) {
	    k = (n >> j) & 0x3F;
	    *out++ = base64_valuetocode[k];
	}
	n = 0;
	data->output_length += 4;

	if (data->output_length >= output_threshold) {
	    PR_ASSERT(data->output_length <= data->output_buflen);
	    if (data->output_fn != NULL) {
		PRInt32 output_result;

		output_result = data->output_fn (data->output_arg,
						 data->output_buffer,
						 (PRInt32) data->output_length);
		if (output_result < 0)
		    return PR_FAILURE;

		out = data->output_buffer;
		data->output_length = 0;
	    } else {
		/*
		 * Check that we are about to exit the loop.  (Since we
		 * are over the threshold, there isn't enough room in the
		 * output buffer for another trip around.)
		 */
		PR_ASSERT(in == end);
		if (in < end) {
		    PR_SetError (PR_BUFFER_OVERFLOW_ERROR, 0);
		    return PR_FAILURE;
		}
	    }
	}
    }

    return PR_SUCCESS;
}

static PRStatus
pl_base64_encode_flush (PLBase64Encoder *data)
{
    int i = data->in_buffer_count;

    if (i == 0 && data->output_length == 0)
	return PR_SUCCESS;

    if (i > 0) {
	char *out = data->output_buffer + data->output_length;
	PRUint32 n;
	int j, k;

	n = ((PRUint32) data->in_buffer[0]) << 16;
	if (i > 1)
	    n |= ((PRUint32) data->in_buffer[1] << 8);

	data->in_buffer_count = 0;

	if (data->line_length > 0) {
	    if (data->current_column >= data->line_length) {
		data->current_column = 0;
		*out++ = B64_CR;
		*out++ = B64_LF;
		data->output_length += 2;
	    }
	}

	/*
	 * This will fill in more than we really have data for, but the
	 * valid parts will end up in the correct position and the extras
	 * will be over-written with pad characters below.
	 */
	for (j = 18; j >= 0; j -= 6) {
	    k = (n >> j) & 0x3F;
	    *out++ = base64_valuetocode[k];
	}

	/* Pad with equal-signs. */
	if (i == 1)
	    out[-2] = B64_PAD;
	out[-1] = B64_PAD;

	data->output_length += 4;
    }

    if (data->output_fn != NULL) {
	PRInt32 output_result;

	output_result = data->output_fn (data->output_arg, data->output_buffer,
					 (PRInt32) data->output_length);
	data->output_length = 0;

	if (output_result < 0)
	    return PR_FAILURE;
    }

    return PR_SUCCESS;
}


/*
 * The maximum space needed to hold the output of the encoder given input
 * data of length "size", and allowing for CRLF added at least every
 * line_length bytes (we will add it at nearest lower multiple of 4).
 * There is no trailing CRLF.
 */
static PRUint32
PL_Base64MaxEncodedLength (PRUint32 size, PRUint32 line_length)
{
    PRUint32 tokens, tokens_per_line, full_lines, line_break_chars, remainder;

    tokens = (size + 2) / 3;

    if (line_length == 0)
	return tokens * 4;

    if (line_length < 4)	/* too small! */
	line_length = 4;

    tokens_per_line = line_length / 4;
    full_lines = tokens / tokens_per_line;
    remainder = (tokens - (full_lines * tokens_per_line)) * 4;
    line_break_chars = full_lines * 2;
    if (remainder == 0)
	line_break_chars -= 2;

    return (full_lines * tokens_per_line * 4) + line_break_chars + remainder;
}


/*
 * A distinct internal creation function for the buffer version to use.
 * (It does not want to specify an output_fn, and we want the normal
 * Create function to require that.)  All common initialization of the
 * encoding context should be done *here*.
 *
 * Save "line_length", rounded down to nearest multiple of 4 (if not
 * already even multiple).  Allocate output_buffer, if not provided --
 * based on given size if specified, otherwise based on line_length.
 */
static PLBase64Encoder *
pl_base64_create_encoder (PRUint32 line_length, char *output_buffer,
			  PRUint32 output_buflen)
{
    PLBase64Encoder *data;
    PRUint32 line_tokens;

    data = PR_NEWZAP(PLBase64Encoder);
    if (data == NULL)
	return NULL;

    if (line_length > 0 && line_length < 4)	/* too small! */
	line_length = 4;

    line_tokens = line_length / 4;
    data->line_length = line_tokens * 4;

    if (output_buffer == NULL) {
	if (output_buflen == 0) {
	    if (data->line_length > 0)	/* need to include room for CRLF */
		output_buflen = data->line_length + 2;
	    else
		output_buflen = 64;		/* XXX what is a good size? */
	}

	output_buffer = (char *) PR_Malloc(output_buflen);
	if (output_buffer == NULL) {
	    PR_Free(data);
	    return NULL;
	}
    }

    data->output_buffer = output_buffer;
    data->output_buflen = output_buflen;
    return data;