commit 41570a8a6d7d842b810b049cb067283df23bc050
parent d96ae84c979ca4198154c5e4ddf44f9ab626355f
Author: Henry Wilson <henry@henryandlizzy.uk>
Date: Mon, 22 Dec 2025 21:13:44 +0000
move cat to .cpp and add file descriptor type
Diffstat:
5 files changed, 55 insertions(+), 44 deletions(-)
diff --git a/cat.c b/cat.c
@@ -1,29 +0,0 @@
-#include "linux.h"
-
-static void cat(int fd)
-{
- static char buf[0x1000];
-
- for (;;)
- {
- int n = read(fd, buf, sizeof(buf));
- if (get_errno(n))
- exit(2);
- if (n == 0)
- return;
- if (write(1, buf, n) != n)
- exit(3);
- }
-}
-
-int main(int argc, char* argv[])
-{
- for (int i = 1; i < argc; ++i)
- {
- int fd = openat(AT_FDCWD, argv[i], 0, O_RDONLY);
- if (get_errno(fd))
- return 1;
- cat(fd);
- close(fd);
- }
-}
diff --git a/cat.cpp b/cat.cpp
@@ -0,0 +1,29 @@
+#include "linux.hpp"
+
+static void cat(filedesc fd)
+{
+ static char buf[0x1000];
+
+ for (;;)
+ {
+ int n = read(fd, buf, sizeof(buf));
+ if (get_errno(n))
+ exit(2);
+ if (n == 0)
+ return;
+ if (write(stdout, buf, n) != n)
+ exit(3);
+ }
+}
+
+int main(int argc, char* argv[])
+{
+ for (int i = 1; i < argc; ++i)
+ {
+ filedesc fd = openat(AT_FDCWD, argv[i], 0, O_RDONLY);
+ if (!fd)
+ return 1;
+ cat(fd);
+ close(fd);
+ }
+}
diff --git a/linux.hpp b/linux.hpp
@@ -60,23 +60,29 @@ struct span
{}
};
+struct filedesc
+{
+ int num = -1;
+ inline operator bool() const { return num >= 0; }
+};
+
+filedesc const stdin{0};
+filedesc const stdout{1};
+filedesc const stderr{2};
+
__attribute__((noreturn))
extern void exit(int error_code);
-extern "C" {
-extern int read(int fd, char* data, size_t count);
-}
-extern int read(int fd, span<char> data);
+extern ssize_t read(filedesc fd, char* data, size_t count);
+extern ssize_t read(filedesc fd, span<char> data);
-extern "C" {
-extern int write(int fd, char const* data, size_t count);
-}
-extern int write(int fd, span<char const> data);
-extern ssize_t write(int fd, span<span<char const> const> data);
+extern ssize_t write(filedesc fd, char const* data, size_t count);
+extern ssize_t write(filedesc fd, span<char const> data);
+extern ssize_t write(filedesc fd, span<span<char const> const> data);
-extern int openat(int fd, char const* name, int flags, int mode);
+extern filedesc openat(int fd, char const* name, int flags, int mode);
-extern int close(int fd);
+extern int close(filedesc fd);
struct linux_dirent64 {
ino64_t d_ino; /* 64-bit inode number */
diff --git a/test.cpp b/test.cpp
@@ -6,14 +6,14 @@ char bss[4];
void text()
{
- write(1, {rodata, sizeof(rodata) - 1});
- write(1, {data, sizeof(data) - 1});
+ write(stdout, {rodata, sizeof(rodata) - 1});
+ write(stdout, {data, sizeof(data) - 1});
bss[0] = 'b';
bss[1] = 's';
bss[2] = 's';
bss[3] = '\n';
- write(1, bss);
+ write(stdout, bss);
}
int main()
diff --git a/x86_64.s b/x86_64.s
@@ -45,13 +45,16 @@ syscall6:
ret
extern read
+extern_alias _Z4read8filedescPcy
_syscall 0 syscall3
extern write
-extern_alias _Z5writei4spanIKcE
+extern_alias _Z5write8filedescPKcy
+extern_alias _Z5write8filedesc4spanIKcE
_syscall 1 syscall3
extern close
+extern_alias _Z5close8filedesc
_syscall 3 syscall3
extern mmap
@@ -66,10 +69,12 @@ extern_alias _Z9nanosleepPK8timespecPS_
_syscall 35 syscall3
extern exit
+extern_alias _Z4exiti
_syscall 60 syscall3
extern getdents64
_syscall 217 syscall3
extern openat
+extern_alias _Z6openatiPKcii
_syscall 257 syscall6
