Add iso_file_src default implementation.

This will be the base class for file content writting, with support for 
on-the-file file modification, useful for things like compression or 
encryption.

libisofs/file_src.c

@@ -0,0 +1,163 @@
+#include <stdlib.h>       
+#include <stdio.h>       
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
+#include <string.h>
+#include <limits.h>
+
+#include "file_src.h"
+#include "messages.h"
+
+#define BLOCK_SIZE 2048
+
+struct local_file_data {
+	int fd; /* the file descriptor, once the file is opened */
+	off_t size; /* file size */
+	off_t bytes_read; /* bytes already read from file */
+	int error;
+	char *path; /* path of the file on local filesystem */
+};
+
+static
+int lf_open(struct iso_file_src *src)
+{
+	struct local_file_data *data;
+	assert(src);
+	
+	data = (struct local_file_data*) src->data;
+	
+	assert(data->fd == -1);
+	
+	data->fd = open(data->path, O_RDONLY);
+	data->bytes_read = (off_t) 0;
+	data->error = 0;
+	return (data->fd != -1 ? 1 : 0);
+}
+
+static
+void lf_close(struct iso_file_src *src)
+{
+	struct local_file_data *data;
+	assert(src);
+	
+	data = (struct local_file_data*) src->data;
+	assert(data->fd != -1);
+	
+	close(data->fd);
+	data->fd = -1;
+}
+
+static
+int lf_read_block(struct iso_file_src *src, unsigned char *buffer)
+{
+	ssize_t bytes;
+	struct local_file_data *data;
+	assert(src);
+	assert(buffer);
+	
+	data = (struct local_file_data*) src->data;
+	assert(data->fd != -1);
+	
+	if (data->bytes_read >= data->size) {
+		return 0;
+	}
+	
+	if (data->error) {
+		memset(buffer, 0, BLOCK_SIZE);
+		data->bytes_read += BLOCK_SIZE;
+		return -2;
+	}
+	
+	bytes = 0;
+	
+	do {
+		ssize_t result;
+		result = read(data->fd, buffer + bytes, BLOCK_SIZE - bytes);
+		if (result < 0) {
+			char msg[PATH_MAX + 32];
+			sprintf(msg, "Problem reading from %s", data->path);
+			iso_msg_sorry(LIBISO_CANT_READ_FILE, msg);
+			
+			/* fill buffer with 0s and return */ 
+			memset(buffer + bytes, 0, BLOCK_SIZE - bytes);
+			data->bytes_read += BLOCK_SIZE;
+			return -1;
+		}
+		if (!result)
+			break;
+		bytes += result;	
+	} while (bytes < BLOCK_SIZE);
+	
+	if (bytes < BLOCK_SIZE) {
+		/* eof */
+		memset(buffer + bytes, 0, BLOCK_SIZE - bytes);
+	}
+	
+	data->bytes_read += (off_t) bytes;
+	if (data->bytes_read >= data->size) {
+		return 0;
+	} else {
+		return 1;
+	}
+}
+
+static
+off_t lf_get_size(struct iso_file_src *src)
+{
+	struct local_file_data *data;
+	assert(src);
+	
+	data = (struct local_file_data*) src->data;
+	return data->size;
+}
+
+static
+void lf_free_data(struct iso_file_src *src)
+{
+	free(src->data);
+}
+
+struct iso_file_src* 
+iso_file_src_from_path(const char *path)
+{
+	struct stat info;
+	struct iso_file_src *src;
+	struct local_file_data *data;
+	
+	assert(path);
+	
+	if (lstat(path, &info) < 0) {
+		iso_msg_fatal(LIBISO_FILE_DOESNT_EXIST, "File doesn't exist");
+		return NULL;
+	}
+	if (access(path, R_OK) < 0) {
+		iso_msg_fatal(LIBISO_FILE_NO_READ_ACCESS, "No read access");
+		return NULL;
+	}
+	
+	data = malloc(sizeof(struct local_file_data));
+	if (!data)
+		return NULL;
+	
+	src = malloc(sizeof(struct iso_file_src));	
+	if (!src) {
+		free(data);
+		return NULL;
+	}
+	
+	data->fd = -1;
+	data->path = strdup(path);
+	data->size = info.st_size;
+	
+	src->open = lf_open;
+	src->close = lf_close;
+	src->read_block = lf_read_block;
+	src->get_size = lf_get_size;
+	src->free_data = lf_free_data;
+	
+	src->data = data;
+	return src;
+}