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|
/*= -*- c-file-style: "bsd" -*-
* rproxy -- dynamic caching and delta update in HTTP
* $Id: inhale.c,v 1.16 2000/08/07 08:37:17 mbp Exp $
*
* Copyright (C) 2000 by Martin Pool <mbp@humbug.org.au>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
| I think if you've ordered
| somebody to do something
| you should probably resist
| the urge to thank them.
| -- abc.net.au/thegames/
*/
/*
* TODO: Inhale from a mapptr, rather than doing hard IO because bad
* things happen if it stops short.
*/
#include "includes.h"
#include "command.h"
#include "protocol.h"
#include "prototab.h"
#include "mapptr.h"
#include "inhale.h"
#ifndef __LCLINT__
/* On Linux/glibc this file contains constructs that confuse lclint. */
# include <netinet/in.h> /* ntohs, etc */
#endif /* __LCLINT__ */
#include "varint.h"
#ifdef HAVE_SYS_ENDIAN_H
# include <sys/endian.h>
#endif
/* For debugging porpoises, here are some human-readable forms. */
struct hs_op_kind_name const _hs_op_kind_names[] = {
{"EOF", op_kind_eof },
{"COPY", op_kind_copy },
{"LITERAL", op_kind_literal },
{"SIGNATURE", op_kind_signature },
{"CHECKSUM", op_kind_checksum },
{"INVALID", op_kind_invalid },
{NULL, 0 }
};
/*
* Return a human-readable name for KIND.
*/
char const *
_hs_op_kind_name(hs_op_kind_t kind)
{
const struct hs_op_kind_name *k;
for (k = _hs_op_kind_names; k->kind; k++) {
if (k->kind == kind) {
return k->name;
}
}
return NULL;
}
/*
* Extract parameters from a command starting in memory at P,
* and with format described by ENT.
*/
static void
_hs_parse_command(byte_t const *p,
hs_prototab_ent_t const *ent,
int *param1, int *param2)
{
p++; /* skip command byte */
*param1 = _hs_read_varint(p, ent->len_1);
p += ent->len_1;
if (ent->len_2) {
*param2 = _hs_read_varint(p, ent->len_2);
}
}
/*
* Try to map LEN bytes. If we succeed, *P points to the data and
* LEN is the amount mapped.
*
* If there is not enough data yet, or if we hit EOF, or if something
* breaks, then return HS_FAILED or HS_AGAIN
*/
static hs_result_t
_hs_inhale_map_cmd(hs_map_t *map, off_t input_pos, byte_t const **p,
size_t *len)
{
size_t require_len;
int reached_eof;
require_len = *len;
*p = hs_map_ptr(map, input_pos, len, &reached_eof);
if (!*p) {
_hs_error("couldn't map command byte");
return HS_FAILED;
} else if (*len < require_len && reached_eof) {
/* This is a warning condition, because we shouldn't just run
* off the end of the file; instead we should get an EOF
* command and stop smoothly. */
_hs_error("reached eof when trying to read command byte");
return HS_FAILED;
} else if (*len < require_len) {
/* Perhaps we just couldn't get enough data this time? */
_hs_trace("only mapped %d bytes towards a command header, require %d",
*len, require_len);
return HS_AGAIN;
}
return HS_DONE;
}
/*
* Read a command from MAP, containing a token sequence. The input
* cursor is currently at *INPUT_POS, which is updated to reflect the
* amount of data read.
*
* KIND identifies the kind of command, and if applicable LEN and OFF
* describe the parameters to the command.
*
* If the input routine indicates that it would block, then we return
* without updating the file cursor. Then when we come back later, we
* can try and map at the same position. We know that that data will
* still be available, so we can re-read the whole command.
* Rescanning it is slightly redundant, but easier than worrying about
* finding a place to explicitly store the state.
*
* We first try to map at least one byte, being the command byte.
* This tells us how many bytes will be required for the command and
* its parameters, so if necessary we then try to map that many bytes.
* Then we have the whole command and can interpret it.
*
* Returns HS_DONE, HS_AGAIN or HS_FAILED.
*/
hs_result_t
_hs_inhale_command_map(hs_map_t *map, off_t *input_pos,
hs_op_kind_t *kind,
int *param1, int *param2)
{
const byte_t *cmd;
hs_result_t result;
const hs_prototab_ent_t *ent;
size_t len;
/* First, map at least one byte to find the command type. */
len = 1;
result = _hs_inhale_map_cmd(map, *input_pos, &cmd, &len);
if (result != HS_DONE)
return result;
/* Now find out what this command means */
ent = &_hs_prototab[*cmd];
*kind = ent->kind;
_hs_trace("inhaled initial byte %#04x, kind=%s, total length will be %d",
*cmd, _hs_op_kind_name(*kind), ent->total_size);
if (ent->total_size == 1) {
/* this is an immediate-parameter command byte: really easy */
*param1 = ent->immediate;
*input_pos += 1;
return HS_DONE;
}
if (len < ent->total_size) {
/* read in enough input data to cover all the parameters */
len = ent->total_size;
result = _hs_inhale_map_cmd(map, *input_pos, &cmd, &len);
if (result != HS_DONE)
return result;
}
/* otherwise, we have to make sure we map the whole command header
* now that we know the length */
_hs_parse_command(cmd, ent, param1, param2);
*input_pos += ent->total_size;
/* Now we know we have at least one command byte */
return HS_DONE;
}
|
