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feuille/bin.c

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/*
* bin.c
* Pastes handling.
*
* Copyright (c) 2022
* Tom MTT. <tom@heimdall.pm>
*
* This file is licensed under the 3-Clause BSD License.
* You should have received a copy of the 3-Clause BSD License
* along with this program. If not, see
* <https://basedwa.re/tmtt/feuille/src/branch/main/LICENSE>.
*/
#include "bin.h"
#include <errno.h> /* for errno */
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#include <stdio.h> /* for NULL, fclose, fopen, fputs, snprintf, FILE */
#include <stdlib.h> /* for calloc, free, malloc, rand, realloc */
#include <string.h> /* for strlen */
#include <unistd.h> /* for access, F_OK */
#include "feuille.h" /* for Settings, settings */
/* symbols used to generate IDs */
static char *id_symbols = "abcdefghijklmnopqrstuvwxyz0123456789";
/**
* Generate a random ID, until one is available on disk.
* min_length: the minimum ID length. Will be increased if a collision occurs.
* -> a pointer to the ID. Needs to be freed.
*/
char *generate_id(int min_length)
{
int length = min_length;
/* allocate a buffer to store the ID */
char *buffer;
if ((buffer = malloc((length + 1) * sizeof(char))) == NULL)
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return NULL;
/* for each letter, generate a random one */
for (int i = 0; i < length; i++) {
if (i > 8 * min_length) {
errno = EFBIG;
free(buffer);
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return NULL;
}
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buffer[i] = id_symbols[rand() % strlen(id_symbols)];
buffer[i + 1] = 0;
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/* collision? */
if (i == length - 1 && paste_exists(buffer)) {
/* add one to the ID length and re-allocate the buffer */
length++;
void *tmp;
if ((tmp = realloc(buffer, (length + 1) * sizeof(char))) == NULL) {
free(buffer);
return NULL;
}
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buffer = tmp;
}
}
return buffer;
}
/**
* Check if an ID is already used.
* id: the ID in question.
* -> 1 if exists, 0 if not.
*/
int paste_exists(char *id)
{
return access(id, F_OK) == 0;
}
/**
* Write the paste content to disk.
* paste: the string containing the paste.
* id: the ID of the paste.
* -> 0 if done, -1 if not.
*/
int write_paste(char *paste, char *id)
{
/* open the file with write access */
FILE *file;
if ((file = fopen(id, "w")) == NULL)
return -1;
/* write the content to file */
if (fputs(paste, file) == -1) {
fclose(file);
return -1;
}
/* close the file (obviously) */
fclose(file);
return 0;
}
/**
* Make the full URL for the paste.
* id: the ID of the paste.
* -> a pointer to the URL. Needs to be freed.
*/
char *create_url(char *id)
{
/* calculate the length of the URL */
/* the 3 characters added are the trailing slash, newline and null byte */
int length = strlen(id) + strlen(settings.url) + 3;
/* allocate a buffer to store the URL */
char *buffer;
if ((buffer = malloc(length * sizeof(char))) == NULL)
return NULL;
/* set the buffer to the actual URL */
snprintf(buffer, length, "%s/%s\n", settings.url, id);
return buffer;
}