Made cat faster and slightly bigger

slimcat.1

@@ -1,4 +1,4 @@
-.TH SLIMCAT "1" "August 2020" "SLIM CAT 1.1.0" "User Commands"
+.TH SLIMCAT "1" "August 2020" "SLIM CAT 1.2.0" "User Commands"
 .SH NAME
 slimcat \- still concatenating files and printing on the standard output, just slimmer.
 .SH SYNOPSIS
@@ -8,7 +8,7 @@ slimcat \- still concatenating files and printing on the standard output, just s
 .PP
 This is a rewrite of GNU cat where the unused features are removed. The only option is -h for help and -u for unbuffered output.
 .PP
-We concatenate files(s) to standard output with less than 50 lines of code.
+We concatenate files(s) to standard output with less than 60 lines of code.
 .PP
 With no file, or when file is \-, read standard input.
 .SH EXAMPLES
@@ -37,6 +37,10 @@ Unknown command line argument.
 .TP
 3
 Error while writing.
+.TP
+4
+Error while allocating memory.
+
 .SH AUTHOR
 Written by Adam McKenney
 .SH "REPORTING BUGS"

src/cat.c

@@ -3,36 +3,46 @@
 #include <stdio.h> //fprintf, perror
 #include <stdlib.h> //exit
 #include <unistd.h> //read, write, close
-#include <fcntl.h> //open
+#include <sys/types.h> //stat
+#include <sys/stat.h> //stat
+#include <sys/sendfile.h> //sendfile
+#include <fcntl.h> //open, STDIN_FILENO, STDOUT_FILENO
 
 #define NAME "slimcat"   //Program name, can be changed so a user can keep their bloated version of cat
 #define HELP "Usage: " NAME " [-hu] [file...]\nWe concatenate files(s) to standard output with less than 50 lines of code.\n\nWith no file, or when file is -, read standard input.\nExamples:\n  " NAME " -h     Displays the help\n  " NAME " -u     Tells the OS that we dont want a buffer (warning may be a lot slower with a large file).\n  " NAME " x - y  Output x's contents, then standard input, then y's contents.\n  " NAME "        Copy standard input to standard output."
 #define BUFF_SIZE 10000 //a larger buffer trades memory for speed
 
-void throw_error(char* extra_msg, int exit_code){
+void throw_error(const char* extra_msg, const int exit_code){
 /* function to writes the program name, optionally extra info, then the error to stderr */
 	if(extra_msg != NULL) fprintf(stderr, "%s: %s: ", NAME, extra_msg);
 	else fprintf(stderr, "%s: ", NAME);
 	perror("");
 	if(exit_code) exit(exit_code); //allows non-fatal errors to keep going
 }
-void cat(int fd, char no_buf){
+void cat(const int fd, const char no_buf, size_t size){
 /* reads from the file descriptor into buf, until zero bytes are read  */
-	char buf[BUFF_SIZE];
-	size_t r = 0, size = BUFF_SIZE;
-	if(no_buf) size = sizeof(char);
-	while((r=read(fd, buf, size)) > 0)
-		if(write(1, buf, r) != r) throw_error(NULL, 3); //if writing stops for some reason
-	if(r == -1) throw_error(NULL, 1); //if read(2) throws an error
+	if(fd == STDIN_FILENO || size > 2147479552 /* max file size for sendfile in Linux */ ){
+		size_t r = 0;
+		if(no_buf) size = 1;
+		void *buf = malloc(size);
+		if(buf == NULL) throw_error("Buffer Allocation", 4);
+		while((r=read(fd, buf, size)) > 0)
+			if(write(STDOUT_FILENO, buf, r) != r) throw_error(NULL, 3); //if writing stops for some reason
+		if(r == -1) throw_error(NULL, 1); //if read(2) throws an error
+		free(buf);
+	} else //if we are given a file, use the sendfile syscall for better speed
+		if(sendfile(STDOUT_FILENO, fd, 0, size) != size) throw_error("In sendfile", 1);
 }
-int get_file(char* file_name, char no_buf){
+void get_file(const char* file_name, const char no_buf){
 /* tries to open the user's file, then calls cat() with its file pointer */
-	int fd = -1;
+	if(file_name[0] == '-' && file_name[1] == '\0'){ cat(STDIN_FILENO, no_buf, BUFF_SIZE); return;}
+	struct stat buffer;
+	int fd = -1, status = stat(file_name, &buffer);
+	if(status != 0) throw_error(file_name, 1);
 	fd = open(file_name, O_RDONLY);
 	if(fd == -1) throw_error(file_name, 1);
-	cat(fd, no_buf);
+	cat(fd, no_buf, buffer.st_size);
 	close(fd);
-	return 0;
 }
 int main(int argc, char *argv[]){
 	size_t i = 0;
@@ -42,10 +52,10 @@ int main(int argc, char *argv[]){
 			if(argv[i][1] == 'h') { puts(HELP); return 0; }
 			else if(argv[i][1] == 'u') no_buf = 1; //required by POSIX, turns off buffered output
 			else { fprintf(stderr, "%s: unknown command line arg '%s'\n", NAME, argv[i]); return 2;}
-		} else break;
+		} else {
+			if(argv[i] == NULL || argv[i][0] == '-') cat(STDIN_FILENO, no_buf, BUFF_SIZE); //if no args
+			else for( ; i < argc; i++) get_file(argv[i], no_buf); //step through each arg as if it's a file
+		}
 	}
-	if(argv[i] == NULL) cat(STDIN_FILENO, no_buf); //if no args
-	else for( ; i < argc; i++) get_file(argv[i], no_buf); //step through each arg as if it's a file
 	return 0;
 }
-