1 files changed, 147 insertions, 0 deletions
diff --git a/src/block.c b/src/block.c
new file mode 100644
index 0000000..a6c919d
--- /dev/null
+++ b/src/block.c
@@ -0,0 +1,147 @@
+#include "block.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "config.h"
+#include "util.h"
+
+block block_new(const char *const icon, const char *const command,
+                const unsigned int interval, const int signal) {
+    block block = {
+        .icon = icon,
+        .command = command,
+        .interval = interval,
+        .signal = signal,
+
+        .output = {[0] = '\0'},
+        .fork_pid = -1,
+    };
+
+    return block;
+}
+
+int block_init(block *const block) {
+    if (pipe(block->pipe) != 0) {
+        (void)fprintf(stderr,
+                      "error: could not create a pipe for \"%s\" block\n",
+                      block->command);
+        return 1;
+    }
+
+    return 0;
+}
+
+int block_deinit(block *const block) {
+    int status = close(block->pipe[READ_END]);
+    status |= close(block->pipe[WRITE_END]);
+    if (status != 0) {
+        (void)fprintf(stderr, "error: could not close \"%s\" block's pipe\n",
+                      block->command);
+        return 1;
+    }
+
+    return 0;
+}
+
+int block_execute(block *const block, const uint8_t button) {
+    // Ensure only one child process exists per block at an instance.
+    if (block->fork_pid != -1) {
+        return 0;
+    }
+
+    block->fork_pid = fork();
+    if (block->fork_pid == -1) {
+        (void)fprintf(
+            stderr, "error: could not create a subprocess for \"%s\" block\n",
+            block->command);
+        return 1;
+    }
+
+    if (block->fork_pid == 0) {
+        const int write_fd = block->pipe[WRITE_END];
+        int status = close(block->pipe[READ_END]);
+
+        if (button != 0) {
+            char button_str[4];
+            (void)snprintf(button_str, LEN(button_str), "%hhu", button);
+            status |= setenv("BLOCK_BUTTON", button_str, 1);
+        }
+
+        const char null = '\0';
+        if (status != 0) {
+            (void)write(write_fd, &null, sizeof(null));
+            exit(EXIT_FAILURE);
+        }
+
+        FILE *const file = popen(block->command, "r");
+        if (file == NULL) {
+            (void)write(write_fd, &null, sizeof(null));
+            exit(EXIT_FAILURE);
+        }
+
+        // Ensure null-termination since fgets() will leave buffer untouched on
+        // no output.
+        char buffer[LEN(block->output)] = {[0] = null};
+        (void)fgets(buffer, LEN(buffer), file);
+
+        // Remove trailing newlines.
+        const size_t length = strcspn(buffer, "\n");
+        buffer[length] = null;
+
+        // Exit if command execution failed or if file could not be closed.
+        if (pclose(file) != 0) {
+            (void)write(write_fd, &null, sizeof(null));
+            exit(EXIT_FAILURE);
+        }
+
+        const size_t output_size =
+            truncate_utf8_string(buffer, LEN(buffer), MAX_BLOCK_OUTPUT_LENGTH);
+        (void)write(write_fd, buffer, output_size);
+
+        exit(EXIT_SUCCESS);
+    }
+
+    return 0;
+}
+
+int block_update(block *const block) {
+    char buffer[LEN(block->output)];
+
+    const ssize_t bytes_read =
+        read(block->pipe[READ_END], buffer, LEN(buffer));
+    if (bytes_read == -1) {
+        (void)fprintf(stderr,
+                      "error: could not fetch output of \"%s\" block\n",
+                      block->command);
+        return 2;
+    }
+
+    // Collect exit-status of the subprocess to avoid zombification.
+    int fork_status = 0;
+    if (waitpid(block->fork_pid, &fork_status, 0) == -1) {
+        (void)fprintf(stderr,
+                      "error: could not obtain exit status for \"%s\" block\n",
+                      block->command);
+        return 2;
+    }
+    block->fork_pid = -1;
+
+    if (fork_status != 0) {
+        (void)fprintf(stderr,
+                      "error: \"%s\" block exited with non-zero status\n",
+                      block->command);
+        return 1;
+    }
+
+    (void)strncpy(block->output, buffer, LEN(buffer));
+
+    return 0;
+}