feat: add simple inotify prototype

Makefile

@@ -4,15 +4,22 @@
 .POSIX:
 
 NAME=sci
+DESCRIPTION=$(NAME) is a simple contiuous integration system.
 VERSION = 0.1.0
 
-SRC = src/sci.c
-OBJ = $(SRC:.c=.o)
+CC = gcc
 OUTDIR := out/
 OBJDIR := out/obj
 BINDIR := out/bin
-CFLAGS += -DSCI_VERSION="\"$(VERSION)\"" -DSCI_NAME="\"$(NAME)\""
-CFLAGS += -Wall -Werror
+# defs
+CFLAGS += -DSCI_VERSION="\"$(VERSION)\""
+CFLAGS += -DSCI_NAME="\"$(NAME)\""
+CFLAGS += -DSCI_DESCRIPTION="\"$(DESCRIPTION)\""
+# compiler flags
+CFLAGS += -Wall -Werror -std=c23 -g
+# includes
+CFLAGS += -Iinclude
+# libraries
 
 .PHONY: all clean
 
@@ -21,11 +28,14 @@ all: out/bin/sci
 out/obj/%.o: src/%.c | $(OBJDIR)
 	$(CC) -c $? $(CFLAGS) -o $@
 
-out/bin/sci: out/obj/main.o | $(BINDIR)
-	$(CC) -o $@ $(CFLAGS) $+
+OBJ += out/obj/main.o
+OBJ += out/obj/cli.o
+OBJ += out/obj/notify.o
+out/bin/sci: $(OBJ) | $(BINDIR)
+	$(CC) -o $@ $(CFLAGS) $^
 
 clean:
-	rm -rf build
+	rm -rf $(OUTDIR)
 
 $(OUTDIR):
 	mkdir -p $@

README.md

@@ -77,5 +77,20 @@ I also choose `Makefile`s! - Just to force myself to use another build system th
 If you want `compile_commands.json` files, you should use [bear](https://github.com/rizsotto/Bear) as it works well
 
 ### Progress
- - [ ] Zeroth things first, let's create a simple CLI application with `--verbosity VAL` and `--help` options.
- - [ ] First things first, let's implement something that reacts when some provided file changes.
+ - [x] Zeroth things first, let's create a simple CLI application with `--verbosity VAL` and `--help` options.
+ - [x] First things first, let's implement something that reacts when some provided file changes (not poll please).
+ - [ ] Second things second, implement a simple logging system with differing levels of verbosity and configurable 
+       output file using cli options.
+ - [ ] Third things third, implement a thing that simultaneously watches two different files (multithreading).
+ - [ ] Fourth things fourth, implement a prototype that reads a space-separated file and populates a struct.
+
+### Note Regarding `inotify` usage
+From the manpage:
+```
+With careful programming, an application can use inotify to efficiently monitor and cache the state of a set of
+filesystem  objects.  However, robust applications should allow for the fact that bugs in the monitoring logic or races
+of the kind described below may leave the cache inconsistent with the filesystem state.  It is probably wise to do some
+consistency checking, and re‐build the cache when inconsistencies are detected.
+```
+i.e., we should _also_ poll the watched files every once in a while (maybe once per minute? idk) to ensure that we catch
+all events.

include/cli.h

@@ -0,0 +1,25 @@
+#ifndef SCI_CLI_H
+#define SCI_CLI_H
+#include <stdio.h>
+#include "optional.h"
+
+struct cli_options {
+    optional_str file;
+    int verbosity;
+    bool help;
+    bool version;
+};
+
+// Construct a new cli_options struct instance.
+struct cli_options new_options();
+
+// Delete a cli_options struct instance.
+void free_options(struct cli_options v);
+
+// Print the help message.
+void print_help(FILE * out, char* prog_name);
+
+// Parse the command line arguments and give a new cli_options struct instance.
+struct cli_options parse(int argc, char** argv);
+
+#endif

include/notify.h

@@ -0,0 +1,11 @@
+#ifndef SCI_NOTIFY_H
+#define SCI_NOTIFY_H
+#include <sys/inotify.h>
+
+typedef void(*notify_callback)(struct inotify_event* const);
+
+// Start listening for changes to the provided file.
+// Note that the `struct inotify_event*` provided is a managed pointer.
+void listen_for_changes(const char* filename, notify_callback callback);
+
+#endif

include/optional.h

@@ -0,0 +1,11 @@
+#ifndef SCI_OPTIONAL_H
+#define SCI_OPTIONAL_H
+#include <stdbool.h>
+
+#define optional_type(type) struct { bool has_value; type value; }
+typedef optional_type(int) optional_int;
+typedef optional_type(float) optional_float;
+typedef optional_type(char*) optional_str;
+typedef optional_type(const char*) optional_cstr;
+
+#endif

include/util.h

@@ -0,0 +1,17 @@
+#ifndef SCI_UTIL_H
+#define SCI_UTIL_H
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/errno.h>
+#include <unistd.h>
+
+#define ASSERT_SYSCALL_SUCCESS(fd) \
+    do { \
+        if ((fd) == -1) { \
+            fprintf(stderr, "Assertion failed: %s, errno: %d, error: %s\n", #fd, errno, strerror(errno)); \
+            assert(fd != -1); \
+        } \
+    } while (0)
+
+#endif

src/cli.c

@@ -0,0 +1,67 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include "cli.h"
+
+struct cli_options new_options() {
+    struct cli_options result;
+    result.file.has_value = false;
+    result.verbosity = 1;
+    result.help = false;
+    result.version = false;
+    return result;
+}
+
+void free_options(struct cli_options v) {
+    if(v.file.has_value)
+        free(v.file.value);
+}
+
+//                                                         <max
+const char* optstring = "f:v:hV";
+const char* help_msg = 
+    "Usage: %s [-v level] [-h] [-V]\n"
+    "\n"
+    SCI_DESCRIPTION "\n"
+    "\n"
+    "THIS PROGRAM IS STILL JUST A PROTOTYPE, AND NOT\n"
+    "ACTUALLY USEFUL YET\n"
+    "\n"
+    "OPTIONS:\n"
+    "  -f file     set file\n"
+    "  -v level    Set verbosity level [0-3]\n"
+    "  -h          Show this message and exit\n"
+    "  -V          Show version and exit\n"
+    ;
+//                                                         <max
+
+void print_help(FILE * out, char* prog_name) {
+    fprintf(out, help_msg, prog_name);
+}
+
+struct cli_options parse(int argc, char** argv) {
+    struct cli_options options = new_options();
+    int opt;
+    while((opt = getopt(argc, argv, optstring)) != -1) {
+        switch(opt) {
+            case 'f':
+                options.file.value = strdup(optarg);
+                options.file.has_value = true;
+                break;
+            case 'v':
+                options.verbosity = atoi(optarg);
+                break;
+            case 'V':
+                options.version = true;
+                break;
+            case 'h':
+                options.help = true;
+                break;
+            default:
+                print_help(stderr, argv[0]);
+                exit(EXIT_FAILURE);
+        }
+    }
+    return options;
+}

src/main.c

@@ -1,64 +1,37 @@
-#include <stdio.h>
+#include "cli.h"
+#include "notify.h"
 #include <stdlib.h>
 #include <unistd.h>
-#include <stdbool.h>
-#include <getopt.h>
 
-struct cli_options {
-    int verbosity;
-    bool help;
-    bool version;
-};
-
-struct cli_options new_options() {
-    struct cli_options result;
-    result.verbosity = 0;
-    result.help = false;
-    return result;
-}
-
-//                                                         <max
-char* help_msg = 
-    "Usage: %s [-v level] [-h] [-V]\n"
-    "\n"
-    SCI_NAME " is a simple contiuous integration system.\n"
-    "\n"
-    "OPTIONS:\n"
-    "  -v level    Set verbosity level [0-3]\n"
-    "  -h          Show this message and exit\n"
-    "  -V          Show version and exit\n"
-    ;
-//                                                         <max
-
-void print_help(FILE * out, char* prog_name) {
-    fprintf(out, help_msg, prog_name);
+void on_notify_event(struct inotify_event* const e) {
+    fprintf(stdout, "got an event:\n");
+    fprintf(stdout, "  wd: %d\n", e->wd);
+    fprintf(stdout, "  mask: %d\n", e->mask);
+    fprintf(stdout, "  cookie: %d\n", e->cookie);
+    fprintf(stdout, "  len: %d\n", e->len);
+    fprintf(stdout, "  name: %s\n", e->name);
 }
 
 int main(int argc, char** argv) {
-    struct cli_options options = new_options();
-    int opt;
-    while((opt = getopt(argc, argv, "v:hV")) != -1) {
-        switch(opt) {
-            case 'v':
-                options.verbosity = atoi(optarg);
-                break;
-            case 'V':
-                options.version = true;
-                break;
-            case 'h':
-                options.help = true;
-                break;
-            default: // '?'
-                print_help(stderr, argv[0]);
-                exit(EXIT_FAILURE);
-        }
-    }
-    if(options.help) {
+    struct cli_options args = parse(argc, argv);
+
+    if(args.help) {
         print_help(stdout, argv[0]);
         exit(EXIT_SUCCESS);
     }
-    if(options.version) {
+
+    if(args.version) {
         fprintf(stdout, SCI_VERSION "\n");
         exit(EXIT_SUCCESS);
     }
+
+    if(args.file.has_value) {
+        if(access(args.file.value, F_OK) != 0) {
+            fprintf(stderr, "no such file or directory %s\n", args.file.value);
+            exit(EXIT_FAILURE);
+        }
+        listen_for_changes(args.file.value, &on_notify_event);
+    }
+
+    free_options(args);
 }

src/notify.c

@@ -0,0 +1,23 @@
+#include "notify.h"
+#include "util.h"
+
+#define EV_SIZE sizeof(struct inotify_event)
+#define BUF_LEN EV_SIZE * 32
+
+void listen_for_changes(const char* filename, notify_callback callback) {
+    int fd = inotify_init();
+    ASSERT_SYSCALL_SUCCESS(fd);
+    inotify_add_watch(fd, filename, IN_ATTRIB);
+
+    fprintf(stdout, "listening for changes in file: %s\n", filename);
+
+    char buffer[BUF_LEN];
+    int r = read(fd, buffer, BUF_LEN);
+    assert(r != -1);
+    for(int i = 0; i < r; ) {
+        struct inotify_event* e = (struct inotify_event*)&buffer[i];
+        callback(e);
+        i += EV_SIZE + e->len;
+    }
+    ASSERT_SYSCALL_SUCCESS(close(fd)); // TODO: have a hashmap of threads (see readme)
+}