From e21df48de15e97c9c9f517754bd23e10cf3e285d Mon Sep 17 00:00:00 2001
From: gbrochar <gaetanbrochard@protonmail.com>
Date: Fri, 15 Mar 2024 15:58:57 +0100
Subject: [PATCH] feat: error handling and header start

---
 Makefile     |  2 ++
 inc/ft_nm.h  |  6 ++++++
 src/error.c  | 11 +++++++++++
 src/header.c | 26 ++++++++++++++++++++++++++
 src/main.c   | 22 +++++++++++++++++-----
 5 files changed, 62 insertions(+), 5 deletions(-)
 create mode 100644 src/error.c
 create mode 100644 src/header.c

diff --git a/Makefile b/Makefile
index 916b12c..8c27cfd 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,8 @@
 NAME = ft_nm
 
 SRC_FILES = main.c \
+			error.c \
+			header.c \
 
 INC_FILES = ft_nm.h \
 
diff --git a/inc/ft_nm.h b/inc/ft_nm.h
index 381febd..835d06c 100644
--- a/inc/ft_nm.h
+++ b/inc/ft_nm.h
@@ -9,4 +9,10 @@
 
 # include "libft.h"
 
+# define FT_NM_SUCCESS 0
+# define FT_NM_FAILURE -1
+
+void ft_nm_error(const char *path);
+int check_header(Elf64_Ehdr *header);
+
 #endif
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..33bae6d
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,11 @@
+#include "ft_nm.h"
+// XXX
+#include <string.h>
+
+void ft_nm_error(const char *path) {
+	char *str = malloc(8 + ft_strlen(path));
+	ft_strcpy(str, "ft_nm: ");
+	ft_strcat(str, path);
+	perror(str);
+	free(str);
+}
diff --git a/src/header.c b/src/header.c
new file mode 100644
index 0000000..6842820
--- /dev/null
+++ b/src/header.c
@@ -0,0 +1,26 @@
+#include "ft_nm.h"
+
+int check_magic_number(Elf64_Ehdr *header) {
+	if (ft_strncmp((void *)&header->e_ident[EI_MAG0], "\x7f""ELF", 4)) {
+		return FT_NM_FAILURE;
+	}
+	return FT_NM_SUCCESS;
+}
+
+int check_format(Elf64_Ehdr *header) {
+	if (header->e_ident[EI_CLASS] == ELFCLASSNONE) {
+		printf("problem\n");
+		return FT_NM_FAILURE;
+	}
+	return FT_NM_SUCCESS;
+}
+
+int check_header(Elf64_Ehdr *header) {
+	if (check_magic_number(header) == FT_NM_FAILURE) {
+		return FT_NM_FAILURE;
+	}
+	if (check_format(header) == FT_NM_FAILURE) {
+		return FT_NM_FAILURE;
+	}
+	return FT_NM_SUCCESS;
+}
diff --git a/src/main.c b/src/main.c
index 32e53a8..e0c6db4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,5 +1,12 @@
 #include "ft_nm.h"
 
+void print_bits(char c) {
+	for (int a = 7; a >= 0; a--) {
+		ft_putnbr(c >> a & 1);
+	}
+	ft_putchar('\n');
+}
+
 int main(int ac, char **av) {
 	char *path = ft_strdup("a.out");
 	if (ac > 1) {
@@ -7,17 +14,22 @@ int main(int ac, char **av) {
 		path = av[1];
 	}
 	int fd = open(path, O_RDONLY);
-	printf("Opening file %s with fd %d\n", path, fd);
+	if (fd == -1) {
+		ft_nm_error(path);
+	}
 	void *ptr = NULL;
 	Elf64_Ehdr *header;
 
 	ptr = mmap(NULL, 64, PROT_READ, MAP_PRIVATE, fd, 0);
 	if (ptr != MAP_FAILED) {
 		header = (Elf64_Ehdr *)ptr;
-		write(1, ptr, 4);
-		write(1, "\n", 1);
-		write(1, header->e_ident, 4);
-		write(1, "\n", 1);
+		if (check_header(header) == FT_NM_FAILURE) {
+			printf("ft_nm: %s: file format not recognized\n", path);
+			exit (1);
+		}
+		for (int i = 0; i < 64; i++) {
+			print_bits(((char *)ptr)[i]);
+		}
 		if (header->e_ident[EI_OSABI] == 0x00) {
 			printf("This ELF is for System V! :)\n");
 		}