Moves files to file-global struct layout.

lib/std/build/WriteFileStep.zig

@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2021 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+const std = @import("../std.zig");
+const build = @import("../build.zig");
+const Step = build.Step;
+const Builder = build.Builder;
+const fs = std.fs;
+const warn = std.debug.warn;
+const ArrayList = std.ArrayList;
+
+const WriteFileStep = @This();
+
+step: Step,
+builder: *Builder,
+output_dir: []const u8,
+files: std.TailQueue(File),
+
+pub const File = struct {
+    source: build.GeneratedFile,
+    basename: []const u8,
+    bytes: []const u8,
+};
+
+pub fn init(builder: *Builder) WriteFileStep {
+    return WriteFileStep{
+        .builder = builder,
+        .step = Step.init(.WriteFile, "writefile", builder.allocator, make),
+        .files = .{},
+        .output_dir = undefined,
+    };
+}
+
+pub fn add(self: *WriteFileStep, basename: []const u8, bytes: []const u8) void {
+    const node = self.builder.allocator.create(std.TailQueue(File).Node) catch unreachable;
+    node.* = .{
+        .data = .{
+            .source = build.GeneratedFile{
+                .step = &self.step,
+                .getPathFn = getFilePath,
+            },
+            .basename = self.builder.dupePath(basename),
+            .bytes = self.builder.dupe(bytes),
+        },
+    };
+
+    self.files.append(node);
+}
+/// Unless setOutputDir was called, this function must be called only in
+/// the make step, from a step that has declared a dependency on this one.
+/// To run an executable built with zig build, use `run`, or create an install step and invoke it.
+//pub const getOutputPath = @compileError("WriteFileStep.getOutputPath is deprecated! Use getFileSource to retrieve a ");
+/// Gets a file source for the given basename. If the file does not exist, returns `null`.
+pub fn getFileSource(step: *WriteFileStep, basename: []const u8) ?build.FileSource {
+    var it = step.files.first;
+    while (it) |node| : (it = node.next) {
+        if (std.mem.eql(u8, node.data.basename, basename))
+            return build.FileSource{ .generated = &node.data.source };
+    }
+    return null;
+}
+
+/// Returns the
+fn getFilePath(source: *const build.GeneratedFile) []const u8 {
+    const file = @fieldParentPtr(File, "source", source);
+    const step = @fieldParentPtr(WriteFileStep, "step", source.step);
+
+    return fs.path.join(
+        step.builder.allocator,
+        &[_][]const u8{ step.output_dir, file.basename },
+    ) catch unreachable;
+}
+
+fn make(step: *Step) !void {
+    const self = @fieldParentPtr(WriteFileStep, "step", step);
+
+    // The cache is used here not really as a way to speed things up - because writing
+    // the data to a file would probably be very fast - but as a way to find a canonical
+    // location to put build artifacts.
+
+    // If, for example, a hard-coded path was used as the location to put WriteFileStep
+    // files, then two WriteFileSteps executing in parallel might clobber each other.
+
+    // TODO port the cache system from stage1 to zig std lib. Until then we use blake2b
+    // directly and construct the path, and no "cache hit" detection happens; the files
+    // are always written.
+    var hash = std.crypto.hash.blake2.Blake2b384.init(.{});
+
+    // Random bytes to make WriteFileStep unique. Refresh this with
+    // new random bytes when WriteFileStep implementation is modified
+    // in a non-backwards-compatible way.
+    hash.update("eagVR1dYXoE7ARDP");
+    {
+        var it = self.files.first;
+        while (it) |node| : (it = node.next) {
+            hash.update(node.data.basename);
+            hash.update(node.data.bytes);
+            hash.update("|");
+        }
+    }
+    var digest: [48]u8 = undefined;
+    hash.final(&digest);
+    var hash_basename: [64]u8 = undefined;
+    _ = fs.base64_encoder.encode(&hash_basename, &digest);
+    self.output_dir = try fs.path.join(self.builder.allocator, &[_][]const u8{
+        self.builder.cache_root,
+        "o",
+        &hash_basename,
+    });
+    // TODO replace with something like fs.makePathAndOpenDir
+    fs.cwd().makePath(self.output_dir) catch |err| {
+        warn("unable to make path {s}: {s}\n", .{ self.output_dir, @errorName(err) });
+        return err;
+    };
+    var dir = try fs.cwd().openDir(self.output_dir, .{});
+    defer dir.close();
+    {
+        var it = self.files.first;
+        while (it) |node| : (it = node.next) {
+            dir.writeFile(node.data.basename, node.data.bytes) catch |err| {
+                warn("unable to write {s} into {s}: {s}\n", .{
+                    node.data.basename,
+                    self.output_dir,
+                    @errorName(err),
+                });
+                return err;
+            };
+        }
+    }
+}