From 0d8d4edde65f94ef5a49df6def21f988c8e6b0ad Mon Sep 17 00:00:00 2001
From: NeikiDev <67499407+NeikiDev@users.noreply.github.com>
Date: Sat, 25 Jul 2026 21:36:09 +0200
Subject: [PATCH] Fix nob_read_entire_file for procfs files and pipes

---
 nob.c                                   |  1 +
 nob.h                                   | 46 +++++++++++++----------
 tests/read_entire_file.c                | 50 +++++++++++++++++++++++++
 tests/read_entire_file.stdout.txt       |  7 ++++
 tests/read_entire_file.win32.stdout.txt |  5 +++
 5 files changed, 89 insertions(+), 20 deletions(-)
 create mode 100644 tests/read_entire_file.c
 create mode 100644 tests/read_entire_file.stdout.txt
 create mode 100644 tests/read_entire_file.win32.stdout.txt

diff --git a/nob.c b/nob.c
index acc56b7..9706439 100644
--- a/nob.c
+++ b/nob.c
@@ -5,6 +5,7 @@ const char *test_names[] = {
     "cmd_redirect",
     "cmd_args_passing",
     "read_entire_dir",
+    "read_entire_file",
     "da_resize",
     "da_last",
     "da_remove_unordered",
diff --git a/nob.h b/nob.h
index 2bdb16b..80c1486 100644
--- a/nob.h
+++ b/nob.h
@@ -2564,36 +2564,42 @@ NOBDEF bool nob_rename(const char *old_path, const char *new_path)
 NOBDEF bool nob_read_entire_file(const char *path, Nob_String_Builder *sb)
 {
     bool result = true;
+    size_t saved_count = sb->count;
+    long long m = 0;
 
     FILE *f = fopen(path, "rb");
-    size_t new_count = 0;
-    long long m = 0;
-    if (f == NULL)                 nob_return_defer(false);
-    if (fseek(f, 0, SEEK_END) < 0) nob_return_defer(false);
+    if (f == NULL) nob_return_defer(false);
+
+    if (fseek(f, 0, SEEK_END) == 0) {
 #ifndef _WIN32
-    m = ftell(f);
+        m = ftell(f);
 #else
-    m = _telli64(_fileno(f));
+        m = _telli64(_fileno(f));
 #endif
-    if (m < 0)                     nob_return_defer(false);
-    if (fseek(f, 0, SEEK_SET) < 0) nob_return_defer(false);
-
-    new_count = sb->count + m;
-    if (new_count > sb->capacity) {
-        sb->items = NOB_DECLTYPE_CAST(sb->items)NOB_REALLOC(sb->items, new_count);
-        NOB_ASSERT(sb->items != NULL && "Buy more RAM lool!!");
-        sb->capacity = new_count;
+        if (fseek(f, 0, SEEK_SET) < 0) nob_return_defer(false);
+        if (m > 0) nob_da_reserve(sb, sb->count + (size_t)m);
+    } else {
+        clearerr(f);
     }
 
-    fread(sb->items + sb->count, m, 1, f);
-    if (ferror(f)) {
-        // TODO: Afaik, ferror does not set errno. So the error reporting in defer is not correct in this case.
-        nob_return_defer(false);
+    for (;;) {
+        nob_da_reserve(sb, sb->count + 1);
+        size_t n = fread(sb->items + sb->count, 1, sb->capacity - sb->count, f);
+        sb->count += n;
+        if (n == 0) {
+            if (ferror(f)) {
+                // TODO: Afaik, ferror does not set errno. So the error reporting in defer is not correct in this case.
+                nob_return_defer(false);
+            }
+            break;
+        }
     }
-    sb->count = new_count;
 
 defer:
-    if (!result) nob_log(NOB_ERROR, "Could not read file %s: %s", path, strerror(errno));
+    if (!result) {
+        sb->count = saved_count;
+        nob_log(NOB_ERROR, "Could not read file %s: %s", path, strerror(errno));
+    }
     if (f) fclose(f);
     return result;
 }
diff --git a/tests/read_entire_file.c b/tests/read_entire_file.c
new file mode 100644
index 0000000..a0ebdeb
--- /dev/null
+++ b/tests/read_entire_file.c
@@ -0,0 +1,50 @@
+#include "shared.h"
+
+size_t error_counter = 0;
+
+void error_counting_log_handler(Nob_Log_Level level, const char *fmt, va_list args)
+{
+    UNUSED(fmt);
+    UNUSED(args);
+    if (level == ERROR) error_counter++;
+}
+
+int main(void)
+{
+    String_Builder sb = {0};
+
+    const char *payload = "first line\nsecond line\n";
+    if (!write_entire_file("file.txt", payload, strlen(payload))) return 1;
+    if (!read_entire_file("file.txt", &sb)) return 1;
+    printf("regular file: read %zu bytes\n", sb.count);
+    printf("%.*s", (int)sb.count, sb.items);
+
+    if (!read_entire_file("file.txt", &sb)) return 1;
+    printf("read again: %zu bytes total\n", sb.count);
+
+    Nob_Log_Handler *saved_log_handler = get_log_handler();
+    set_log_handler(error_counting_log_handler);
+    bool ok = read_entire_file("does-not-exist.txt", &sb);
+    set_log_handler(saved_log_handler);
+    printf("missing file: ok=%s, error_counter=%zu, count=%zu\n", ok ? "true" : "false", error_counter, sb.count);
+
+#ifndef _WIN32
+    if (mkfifo("fifo", 0644) < 0) return 1;
+    pid_t pid = fork();
+    if (pid < 0) return 1;
+    if (pid == 0) {
+        FILE *f = fopen("fifo", "wb");
+        if (f == NULL) _exit(1);
+        fputs("hello through a fifo\n", f);
+        fclose(f);
+        _exit(0);
+    }
+    sb.count = 0;
+    if (!read_entire_file("fifo", &sb)) return 1;
+    if (waitpid(pid, NULL, 0) < 0) return 1;
+    printf("fifo: read %zu bytes\n", sb.count);
+    printf("%.*s", (int)sb.count, sb.items);
+#endif
+
+    return 0;
+}
diff --git a/tests/read_entire_file.stdout.txt b/tests/read_entire_file.stdout.txt
new file mode 100644
index 0000000..8e0e0b8
--- /dev/null
+++ b/tests/read_entire_file.stdout.txt
@@ -0,0 +1,7 @@
+regular file: read 23 bytes
+first line
+second line
+read again: 46 bytes total
+missing file: ok=false, error_counter=1, count=46
+fifo: read 21 bytes
+hello through a fifo
diff --git a/tests/read_entire_file.win32.stdout.txt b/tests/read_entire_file.win32.stdout.txt
new file mode 100644
index 0000000..ceed233
--- /dev/null
+++ b/tests/read_entire_file.win32.stdout.txt
@@ -0,0 +1,5 @@
+regular file: read 23 bytes
+first line
+second line
+read again: 46 bytes total
+missing file: ok=false, error_counter=1, count=46