From f404d75c6050223a3cbbe9b7775700ca291ff93d Mon Sep 17 00:00:00 2001
From: Martin Michalec <martin@michalec.dev>
Date: Sun, 22 Feb 2026 06:18:01 +0300
Subject: add lex example

---
 examples/utils.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 examples/utils.c

(limited to 'examples/utils.c')

diff --git a/examples/utils.c b/examples/utils.c
new file mode 100644
index 0000000..35c8d98
--- /dev/null
+++ b/examples/utils.c
@@ -0,0 +1,77 @@
+// examples/utils.c
+
+#include <stddef.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#include "utils.h"
+
+struct cmmm__sv
+mmap_whole (int fd)
+{
+  struct cmmm__sv sv;
+
+  struct stat st;
+  int ret = fstat (fd, &st);
+  UNUSED (ret);
+  ASSERT_MSG (ret != -1, "fstat: %s", strerror (errno));
+  ASSERT (S_ISREG (st.st_mode));
+
+  posix_fadvise (fd, 0, st.st_size, POSIX_FADV_SEQUENTIAL |
+                                    POSIX_FADV_WILLNEED |
+                                    POSIX_FADV_NOREUSE);
+
+  sv.begin = mmap (NULL, st.st_size, PROT_READ, MAP_PRIVATE |
+                                                MAP_POPULATE |
+                                                MAP_NONBLOCK, fd, 0);
+  ASSERT_MSG (sv.begin != MAP_FAILED, "mmap: %s", strerror (errno));
+  posix_madvise ((void *) sv.begin, st.st_size, MADV_HUGEPAGE | MADV_WILLNEED);
+
+  sv.end = sv.begin + st.st_size;
+
+  return sv;
+}
+
+struct cmmm__sv
+read_until_eof (ARENA arena, int fd)
+{
+  struct arena__checkpoint checkpoint = arena__checkpoint (arena);
+  size_t reserve = 4096;
+
+  size_t read_total = 0;
+  for (;;) {
+    arena__reserve (arena, reserve, 1);
+    ssize_t bytes_read = read (fd,
+                               arena__next_free (arena, 1),
+                               arena__room      (arena, 1));
+
+    if (bytes_read < 0) {
+      DEBUG ("fstat: %s", strerror (errno));
+      arena__rollback_to (arena, checkpoint);
+      return (struct cmmm__sv) {0};
+    }
+
+    if (bytes_read == 0)
+      break;
+
+    read_total += bytes_read;
+
+    arena__allocate_fast (arena, bytes_read, 1);
+    reserve *= 2;
+  }
+
+  if (arena->tail->free == checkpoint.free)
+    return (struct cmmm__sv) {0};
+
+  char *ptr = arena__coalesce_from_fast (arena, checkpoint, read_total);
+  return (struct cmmm__sv) {
+    .begin = ptr,
+    .end   = ptr + read_total,
+  };
+}
+
+// examples/utils.c ends here
-- 
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