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all the functions written so far compile fine, working on Cache_open

This commit is contained in:
Fufu Fang 2019-04-20 02:04:29 +01:00
parent 9f1b963014
commit 7ae6d6fe1b
2 changed files with 180 additions and 79 deletions
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203
src/cache.c
View File

@ -1,30 +1,89 @@
#include "cache.h"
long Cache_read(const char *filepath, long offset, long len)
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#define MAX_PATH_LEN 4096
/**
* \brief The metadata directory
*/
char *META_DIR;
/**
* \brief The data directory
*/
char *DATA_DIR;
/**
* \brief strndup with concatenation
* \details This function creates a new string, and concatenate string a and
* string b together.
* \note The maximum length of string a and string b is half the length of the
* maximum length of the output string.
* \param[in] a the first string
* \param[in] b the second string
* \param[n] c the maximum length of the output string
*/
char *strndupcat(const char *a, const char *b, int n)
{
int na = strnlen(a, n/2);
int nb = strnlen(b, n/2);
int nc = na + nb + 1;
char *c = calloc(nc, sizeof(char));
if (!c) {
fprintf(stderr, "strndupcat(): calloc failure!\n");
}
strncpy(c, a, na);
strncat(c, b, nb);
return c;
}
long Cache_write(const char *filepath, long offset, long len,
const uint8_t *content)
void Cache_init(const char *dir)
{
META_DIR = strndupcat(dir, "meta/", MAX_PATH_LEN);
DATA_DIR = strndupcat(dir, "data/", MAX_PATH_LEN);
}
Cache *Cache_create(const char *filepath, long len)
Cache *Cache_create(const char *fn, long len)
{
}
Cache *Cache_open(const char *fn)
{
Cache *cf = malloc(sizeof(Cache));
char *metafn = strndupcat(META_DIR, fn);
char *datafn = strndupcat(DATA_DIR, fn);
/* Check if both metadata and the data file exist */
if(access(cf->metafn, F_OK ) && access(cf->datafn, F_OK)) {
return NULL;
}
free(metafn);
free(datafn);
}
Cache *Cache_open(const char *filepath)
long Cache_read(const char *fn, long offset, long len, uint8_t *buf)
{
}
long Cache_write(const char *fn, long offset, long len,
const uint8_t *buf)
{
}
void Cache_free(Cache *cf)
{
free(cf->filename);
free(cf->metapath);
free(cf->datapath);
free(cf->seg);
free(cf);
}
@ -32,67 +91,106 @@ void Cache_free(Cache *cf)
int Meta_read(Cache *cf)
{
FILE *fp;
fp = fopen(cf->metapath, "r");
char *metafn = strndupcat(META_DIR, cf->filename, MAX_PATH_LEN);
fp = fopen(metafn, "r");
free(metafn);
int res = 1;
if (!fp) {
/* The metadata file does not exist */
fprintf(stderr, "Meta_read(): fopen(): %s\n", strerror(errno));
return -1;
return 0;
}
fread((void *) &(cf->len), sizeof(long), 1, fp);
fread((void *) &(cf->nseg), sizeof(int), 1, fp);
fread(&(cf->len), sizeof(long), 1, fp);
fread(&(cf->time), sizeof(long), 1, fp);
fread(&(cf->nseg), sizeof(int), 1, fp);
/* Allocate some memory for the segment */
cf->seg = malloc(cf->nseg * sizeof(Seg));
/* Read all the segment */
fread((void *) cf->seg, sizeof(Seg), cf->nseg, fp);
int nmemb = fread(cf->seg, sizeof(Seg), cf->nseg, fp);
/* Simplified error checking */
/* Error checking for fread */
if (ferror(fp)) {
fprintf(stderr,
"Meta_read(): fread(): encountered error (from ferror)!\n");
res = 0;
}
/* Check for inconsistent metadata file */
if (nmemb != cf-> nseg) {
fprintf(stderr,
"Meta_read(): corrupted metadata!\n");
res = 0;
}
if (fclose(fp)) {
fprintf(stderr, "Meta_read(): fclose(): %s\n", strerror(errno));
return -1;
}
return res;
}
int Meta_write(const Cache *cf)
{
FILE *fp;
fp = fopen(cf->metapath, "w");
char *metafn = strndupcat(META_DIR, cf->filename, MAX_PATH_LEN);
fp = fopen(metafn, "w");
free(metafn);
int res = 1;
if (!fp) {
/* The metadata file does not exist */
/* Cannot create the metadata file */
fprintf(stderr, "Meta_write(): fopen(): %s\n", strerror(errno));
return -1;
return 0;
}
/* We log the length of the file just in case */
fwrite((const void *) cf->len, sizeof(long), 1, fp);
fwrite((const void *) cf->nseg, sizeof(int), 1, fp);
fwrite(&(cf->len), sizeof(long), 1, fp);
fwrite(&(cf->time), sizeof(long), 1, fp);
fwrite(&(cf->nseg), sizeof(int), 1, fp);
/* Finally write segments to the file */
fwrite((const void *) cf->seg, sizeof(Seg), cf->nseg, fp);
fwrite(cf->seg, sizeof(Seg), cf->nseg, fp);
/* Simplified error checking */
/* Error checking for fwrite */
if (ferror(fp)) {
fprintf(stderr,
"Meta_write(): fwrite(): encountered error (from ferror)!\n");
res = 0;
}
if (fclose(fp)) {
fprintf(stderr, "Meta_write(): fclose(): %s\n", strerror(errno));
return -1;
}
return res;
}
int Data_create(Cache *cf)
{
int fd;
int mode;
mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
char *datafn = strndupcat(DATA_DIR, cf->filename, MAX_PATH_LEN);
fd = open(datafn, O_WRONLY | O_CREAT, mode);
free(datafn);
if (fd == -1) {
fprintf(stderr, "Data_create(): open(): %s\n", strerror(errno));
return 0;
}
if (ftruncate(fd, cf->len) == -1) {
fprintf(stderr, "Data_create(): ftruncate(): %s\n", strerror(errno));
}
if (close(fd) == -1) {
fprintf(stderr, "Data_create(): close:(): %s\n", strerror(errno));
}
return 1;
}
long Data_read(const Cache *cf, long offset, long len,
uint8_t *buf);
uint8_t *buf)
{
if (len == 0) {
fprintf(stderr, "Data_read(): requested to read 0 byte!\n");
@ -100,10 +198,13 @@ long Data_read(const Cache *cf, long offset, long len,
}
FILE *fp;
fp = fopen(cf->datapath, "r");
char *datafn = strndupcat(DATA_DIR, cf->filename, MAX_PATH_LEN);
fp = fopen(datafn, "r");
free(datafn);
long byte_read = -1;
if (!fp) {
/* The data file does not exist */
/* Failed to open the data file */
fprintf(stderr, "Data_read(): fopen(): %s\n", strerror(errno));
return -1;
}
@ -111,13 +212,13 @@ long Data_read(const Cache *cf, long offset, long len,
if (fseek(fp, offset, SEEK_SET) == -1) {
/* fseek failed */
fprintf(stderr, "Data_read(): fseek(): %s\n", strerror(errno));
return -1;
goto cleanup;
}
long byte_read = fread((void *) buf, sizeof(uint8_t), len, fp);
byte_read = fread(buf, sizeof(uint8_t), len, fp);
if (byte_read != len) {
fprintf(stderr,
"Data_read(): fread(): requested %ld, returned %llu!\n",
"Data_read(): fread(): requested %ld, returned %ld!\n",
len, byte_read);
if (feof(fp)) {
/* reached EOF */
@ -130,14 +231,16 @@ long Data_read(const Cache *cf, long offset, long len,
"Data_read(): fread(): encountered error (from ferror)!\n");
}
}
cleanup:
if (fclose(fp)) {
fprintf(stderr, "Data_read(): fclose(): %s\n", strerror(errno));
return -1;
}
return byte_read;
}
long Data_write(const Cache *cf, long offset, long len,
const uint8_t *buf);
const uint8_t *buf)
{
if (len == 0) {
fprintf(stderr, "Data_write(): requested to write 0 byte!\n");
@ -145,23 +248,27 @@ long Data_write(const Cache *cf, long offset, long len,
}
FILE *fp;
fp = fopen(cf->datapath, "r+");
char *datafn = strndupcat(DATA_DIR, cf->filename, MAX_PATH_LEN);
fp = fopen(datafn, "r+");
free(datafn);
long byte_written = -1;
if (!fp) {
/* The data file does not exist */
/* Failed to open the data file */
fprintf(stderr, "Data_write(): fopen(): %s\n", strerror(errno));
return -1;
}
if (fseek(fp, offset, SEEK_SET) == -1) {
/* fseek failed */
fprintf(stderr, "Data_write(): fseek(): %s\n", strerror(errno));
return -1;
goto cleanup;
}
long byte_written = fwrite((const void *) buf, sizeof(uint8_t), len, fp);
byte_written = fwrite(buf, sizeof(uint8_t), len, fp);
if (byte_written != len) {
fprintf(stderr,
"Data_write(): fwrite(): requested %ld, returned %llu!\n",
"Data_write(): fwrite(): requested %ld, returned %ld!\n",
len, byte_written);
if (feof(fp)) {
/* reached EOF */
@ -174,30 +281,12 @@ long Data_write(const Cache *cf, long offset, long len,
"Data_write(): fwrite(): encountered error (from ferror)!\n");
}
}
cleanup:
if (fclose(fp)) {
fprintf(stderr, "Data_write(): fclose(): %s\n", strerror(errno));
return -1;
}
return byte_written;
}
int Data_create(Cache *cf, long len)
{
int fd;
int mode;
mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
fd = open(cf->filepath, O_WRONLY | O_CREAT, mode);
if (fd == -1) {
fprintf(stderr, "Data_create(): %s\n", strerror(errno));
return 0;
}
if (ftruncate(fd, cf->len) == -1) {
fprintf(stderr, "Data_create(): %s\n", strerror(errno));
return 0;
}
if (close(fd) == -1) {
fprintf(stderr, "Data_create(): %s\n", strerror(errno));
return 0;
}
return 1;
}

56
src/cache.h
View File

@ -1,6 +1,7 @@
#ifndef CACHE_H
#define CACHE_H
#include <stdint.h>
#include <unistd.h>
/**
@ -16,10 +17,6 @@
* - individual segments (array of seg)
*
* \note
* - apologies for whoever is going to be reading this. Sorry for being so
* verbose in this header file, this is probably one of the most challenging
* thing I have ever written so far! Yes I am doing a PhD in computer science,
* but it doesn't imply that I am good at computer science or programming!
* - We are using 'long' to store file size, because the offset in fseek() is
* in long, because the way we use the cache system, you cannot seek past
* long. So the biggest file size has to be able to be stored in long. This
@ -27,7 +24,6 @@
* dependency to fseek().
*/
/**
* \brief a cache segment
*/
@ -41,23 +37,27 @@ typedef struct {
* \note fanf2@cam.ac.uk told me to use an array rather than linked list!
*/
typedef struct {
const char *filename; /**< the filename from the http server */
const char *metapath; /**< the path to the metadata file*/
const char *datapath; /**< the path to the cache file */
char *filename; /**< the filename from the http server */
long len; /**<the size of the file */
long time; /**<the modified time of the file */
int nseg; /**<the number of segments */
Seg *seg; /**< the detail of each segment */
} Cache;
} Cache;
/***************************** To be completed ******************************/
/**
* \brief create a cache file set
*/
Cache *Cache_create(const char *fn, long len);
/**
* \brief Read from a cache file set
* \details This function performs the following two things:
* - check again the metafile to see which segments are available
* - return the available segments
*/
long Cache_read(const char *filepath, long offset, long len);
long Cache_read(const char *fn, long offset, long len, uint8_t *buf);
/**
* \brief Write to a cache file set
@ -65,21 +65,24 @@ long Cache_read(const char *filepath, long offset, long len);
* - Write to the data file
* - Update the metadata file
*/
long Cache_write(const char *filepath, long offset, long len,
const uint8_t *content);
long Cache_write(const char *fn, long offset, long len,
const uint8_t *buf);
/****************************** Work in progress *****************************/
/**
* \brief create a cache file
* \brief open a cache file set
*/
Cache *Cache_create(const char *filepath, long len);
/**
* \brief open a cache file
*/
Cache *Cache_open(const char *filepath);
Cache *Cache_open(const char *fn);
/**************************** Completed functions ****************************/
/**
* \brief initialise the cache system
* \details This function basically sets up the following variables:
* - META_DIR
* - DATA_DIR
*/
void Cache_init(const char *dir);
/**
* \brief free a cache data structure
@ -93,25 +96,34 @@ int Meta_write(const Cache *cf);
/**
* \brief read a metadata file
* \return 0 on error, 1 on success
*/
int Meta_read(Cache *cf);
/**
* \brief create a data file
* \details We use sparse creation here
* \return 1 on success, 0 on failure
* \return
* - 1 on successful creation of the data file, note that the result of
* the ftruncate() is ignored.
* - 0 on failure to create the data file.
*/
int Data_create(Cache *cf, long len);
int Data_create(Cache *cf);
/**
* \brief read a data file
* \return -1 when the data file does not exist
* \return
* - -1 when the data file does not exist
* - otherwise, the number of bytes read.
*/
long Data_read(const Cache *cf, long offset, long len,
uint8_t *buf);
/**
* \brief write to a data file
* \return
* - -1 when the data file does not exist
* - otherwise, the number of bytes written.
*/
long Data_write(const Cache *cf, long offset, long len,
const uint8_t *buf);