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/**
* @file netstring.c Streaming API for netstrings
*
* This file is public domain,
* adapted from https://github.com/PeterScott/netstring-c/"
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include <re.h>
#include "netstring.h"
const char* netstring_error_str(netstring_error err)
{
switch (err) {
case NETSTRING_ERROR_TOO_LONG:
return "NETSTRING_ERROR_TOO_LONG";
case NETSTRING_ERROR_NO_COLON:
return "NETSTRING_ERROR_NO_COLON";
case NETSTRING_ERROR_TOO_SHORT:
return "NETSTRING_ERROR_TOO_SHORT";
case NETSTRING_ERROR_NO_COMMA:
return "NETSTRING_ERROR_NO_COMMA";
case NETSTRING_ERROR_LEADING_ZERO:
return "NETSTRING_ERROR_LEADING_ZERO";
case NETSTRING_ERROR_NO_LENGTH:
return "NETSTRING_ERROR_NO_LENGTH";
default:
return "NETSTRING_ERROR_UNKNOWN";
}
}
/**
* Reads a netstring from a `buffer` of length `buffer_length`. Writes
* to `netstring_start` a pointer to the beginning of the string in
* the buffer, and to `netstring_length` the length of the
* string. Does not allocate any memory. If it reads successfully,
* then it returns 0. If there is an error, then the return value will
* be negative. The error values are:
* NETSTRING_ERROR_TOO_LONG More than 999999999 bytes in a field
* NETSTRING_ERROR_NO_COLON No colon was found after the number
* NETSTRING_ERROR_TOO_SHORT Number of bytes greater than buffer length
* NETSTRING_ERROR_NO_COMMA No comma was found at the end
* NETSTRING_ERROR_LEADING_ZERO Leading zeros are not allowed
* NETSTRING_ERROR_NO_LENGTH Length not given at start of netstring
* If you're sending messages with more than 999999999 bytes -- about
* 2 GB -- then you probably should not be doing so in the form of a
* single netstring. This restriction is in place partially to protect
* from malicious or erroneous input, and partly to be compatible with
* D. J. Bernstein's reference implementation.
* Example:
* if (netstring_read("3:foo,", 6, &str, &len) < 0) explode_and_die();
*/
int netstring_read(char *buffer, size_t buffer_length,
char **netstring_start, size_t *netstring_length)
{
size_t i;
size_t len = 0;
/* Write default values for outputs */
*netstring_start = NULL; *netstring_length = 0;
/* Make sure buffer is big enough. Minimum size is 3. */
if (buffer_length < 3)
return NETSTRING_ERROR_TOO_SHORT;
/* No leading zeros allowed! */
if (buffer[0] == '0' && isdigit(buffer[1]))
return NETSTRING_ERROR_LEADING_ZERO;
/* The netstring must start with a number */
if (!isdigit(buffer[0]))
return NETSTRING_ERROR_NO_LENGTH;
/* Read the number of bytes */
for (i = 0; i < buffer_length && isdigit(buffer[i]); i++) {
/* Error if more than 9 digits */
if (i >= 9)
return NETSTRING_ERROR_TOO_LONG;
/* Accumulate each digit, assuming ASCII. */
len = len*10 + (buffer[i] - '0');
}
/**
* Check buffer length. The buffer must be longer than the sum of:
* - the number we've read.
* - the length of the string itself.
* - the colon.
* - the comma.
*/
if (i + len + 1 >= buffer_length)
return NETSTRING_ERROR_TOO_SHORT;
/* Read the colon */
if (buffer[i++] != ':')
return NETSTRING_ERROR_NO_COLON;
/* Test for the trailing comma, and set the return values */
if (buffer[i + len] != ',')
return NETSTRING_ERROR_NO_COMMA;
*netstring_start = &buffer[i]; *netstring_length = len;
return 0;
}
/**
* Return the number of digits represented in the given number.
* We are assuming that the input is not bigger than NETSTRING_MAX_SIZE.
*/
size_t netstring_num_len(size_t num)
{
char num_str[32];
re_snprintf(num_str, sizeof(num_str), "%zu", num);
return strlen(num_str);
}
/**
* Return the length, in ASCII characters, of a netstring containing
* `data_length` bytes.
*/
size_t netstring_buffer_size(size_t data_length)
{
if (data_length == 0)
return 3;
return netstring_num_len(data_length) + data_length + 2;
}
/*
* Allocate and create a netstring containing the first `len` bytes of `data`.
* This must be manually freed by the client.
* If `len` is 0 then no data will be read from `data`, and it may be NULL.
*/
size_t netstring_encode_new(char **netstring, char *data, size_t len)
{
char *ns;
size_t num_len = 1;
if (len == 0) {
ns = malloc(3);
ns[0] = '0';
ns[1] = ':';
ns[2] = ',';
}
else {
num_len = netstring_num_len(len);
ns = malloc(num_len + len + 2);
sprintf(ns, "%lu:", (unsigned long)len);
memcpy(ns + num_len + 1, data, len);
ns[num_len + len + 1] = ',';
}
*netstring = ns;
return num_len + len + 2;
}
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