From 042e43247f396a9000fead59d9bff87bf12806d6 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Wed, 30 Oct 2024 01:51:14 +0100
Subject: Completely revamp the grab source code

Some of the (many) few changes are:
- Multithreading for significantly faster performance
- The -p/--predicate flag
- Byte offsets as the default
- No customizable colors (maybe this will come back later)
- Newer edition of mlib (formerly librune)
---
 src/tpool.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/tpool.c

(limited to 'src/tpool.c')

diff --git a/src/tpool.c b/src/tpool.c
new file mode 100644
index 0000000..f30bccc
--- /dev/null
+++ b/src/tpool.c
@@ -0,0 +1,127 @@
+/* Thread pool implementation mostly copied from cbs.h */
+
+#include <errno.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <alloc.h>
+#include <array.h>
+#include <errors.h>
+#include <macros.h>
+
+#include "tpool.h"
+#include "work.h"
+
+#include <stdio.h>
+
+static int nproc(void);
+static void *tpwork(void *);
+
+static pthread_t thread_buffer[32];
+
+extern const char *lquot, *rquot;
+
+int
+nproc(void)
+{
+	errno = 0;
+
+	/* Grab the number of processors available on the users system.  If we can
+	   we query sysconf() but fallback to 1 for systems that don’t support the
+	   sysconf() method.  The user can also override this via the GRAB_NPROCS
+	   environment variable, and if that’s invalid then we just issue a
+	   diagnostic and default to 1.
+
+	   We don’t want to error on an invalid value for GRAB_NPROCS because we
+       might be running this tool as part of an editor plugin for example where
+       finding the root cause of your regexp-search failing may not be so
+       trivial. */
+
+	const char *ev = getenv("GRAB_NPROCS");
+	if (ev != nullptr && *ev != 0) {
+		const char *endptr;
+		long n = strtol(ev, (char **)&endptr, 10);
+		if (errno == 0 && *endptr == 0)
+			return (int)n;
+		if (errno != 0)
+			warn("strtol: %s:", ev);
+		if (*endptr != 0)
+			warn("Invalid value for %s%s%s for GRAB_NPROCS", lquot, ev, rquot);
+		return 1;
+	}
+
+#ifdef _SC_NPROCESSORS_ONLN
+	return (int)sysconf(_SC_NPROCESSORS_ONLN);
+#else
+	return 1;
+#endif
+}
+
+int
+tpinit(tpool_t *tp, const char **files, ptrdiff_t filecnt)
+{
+	tp->files = files;
+	tp->filecnt = filecnt;
+	tp->tcnt = nproc();
+	tp->tcnt = MIN(tp->tcnt, filecnt);
+	tp->wi = 0;
+
+	if (tp->tcnt <= 32)
+		tp->thrds = thread_buffer;
+	else if ((tp->thrds = malloc(sizeof(*tp->thrds) * tp->tcnt)) == nullptr)
+		err("malloc:");
+
+	/* If for whatever reason some threads fail to be created, we don’t
+       panic but instead just continue using the threads that were able
+       to spawn.  If all threads fail to spawn we return 0 and the caller
+       will resort to single-threaded behaviour. */
+
+	int n = 0;
+	for (int i = 0; i < tp->tcnt; i++) {
+		if ((errno = pthread_create(tp->thrds + n, nullptr, tpwork, tp)) != 0)
+			warn("failed to create thread:");
+		else
+			n++;
+	}
+	return n;
+}
+
+void
+tpfree(tpool_t *tp)
+{
+	for (int i = 0; i < tp->tcnt; i++)
+		pthread_join(tp->thrds[i], nullptr);
+
+#if DEBUG
+	if (tp->thrds != thread_buffer)
+		free(tp->thrds);
+#endif
+}
+
+void *
+tpwork(void *arg)
+{
+	tpool_t *tp = arg;
+
+	allocator_t mem = init_heap_allocator(nullptr);
+	unsigned char *buf = array_new(mem, typeof(*buf), 4096);
+
+	for (;;) {
+		ptrdiff_t i = atomic_fetch_add(&tp->wi, 1);
+		if (i >= tp->filecnt)
+			break;
+		process_file(tp->files[i], &buf);
+	}
+
+	flockfile(stdout);
+	fwrite(buf, 1, array_len(buf), stdout);
+	funlockfile(stdout);
+
+#if DEBUG
+	array_free(buf);
+#endif
+	return nullptr;
+}
-- 
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