From f7bcc8e04087e2308582d8b6f068e2e71b65bef9 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Thu, 18 Jun 2020 21:08:30 -0400
Subject: rework zig fmt to only make one allocation

taking advantage of the fstat size
---
 lib/std/fs.zig      |  9 ++-------
 lib/std/fs/file.zig | 27 +++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

(limited to 'lib/std')

diff --git a/lib/std/fs.zig b/lib/std/fs.zig
index 262aa4872d..3ff4819ac5 100644
--- a/lib/std/fs.zig
+++ b/lib/std/fs.zig
@@ -1229,14 +1229,9 @@ pub const Dir = struct {
         var file = try self.openFile(file_path, .{});
         defer file.close();
 
-        const size = math.cast(usize, try file.getEndPos()) catch math.maxInt(usize);
-        if (size > max_bytes) return error.FileTooBig;
+        const stat_size = try file.getEndPos();
 
-        const buf = try allocator.allocWithOptions(u8, size, alignment, optional_sentinel);
-        errdefer allocator.free(buf);
-
-        try file.inStream().readNoEof(buf);
-        return buf;
+        return file.readAllAllocOptions(allocator, stat_size, max_bytes, alignment, optional_sentinel);
     }
 
     pub const DeleteTreeError = error{
diff --git a/lib/std/fs/file.zig b/lib/std/fs/file.zig
index ec4059b9c7..0a3c1b5ab7 100644
--- a/lib/std/fs/file.zig
+++ b/lib/std/fs/file.zig
@@ -306,6 +306,33 @@ pub const File = struct {
         try os.futimens(self.handle, &times);
     }
 
+    /// On success, caller owns returned buffer.
+    /// If the file is larger than `max_bytes`, returns `error.FileTooBig`.
+    pub fn readAllAlloc(self: File, allocator: *mem.Allocator, stat_size: u64, max_bytes: usize) ![]u8 {
+        return self.readAllAllocOptions(allocator, stat_size, max_bytes, @alignOf(u8), null);
+    }
+
+    /// On success, caller owns returned buffer.
+    /// If the file is larger than `max_bytes`, returns `error.FileTooBig`.
+    /// Allows specifying alignment and a sentinel value.
+    pub fn readAllAllocOptions(
+        self: File,
+        allocator: *mem.Allocator,
+        stat_size: u64,
+        max_bytes: usize,
+        comptime alignment: u29,
+        comptime optional_sentinel: ?u8,
+    ) !(if (optional_sentinel) |s| [:s]align(alignment) u8 else []align(alignment) u8) {
+        const size = math.cast(usize, stat_size) catch math.maxInt(usize);
+        if (size > max_bytes) return error.FileTooBig;
+
+        const buf = try allocator.allocWithOptions(u8, size, alignment, optional_sentinel);
+        errdefer allocator.free(buf);
+
+        try self.inStream().readNoEof(buf);
+        return buf;
+    }
+
     pub const ReadError = os.ReadError;
     pub const PReadError = os.PReadError;
 
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