port Blob functions

src/browser/webapi/file/Blob.zig

@@ -17,13 +17,258 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 const std = @import("std");
+const Writer = std.Io.Writer;
 
 const js = @import("../../js/js.zig");
+const Page = @import("../../Page.zig");
 
+/// https://w3c.github.io/FileAPI/#blob-section
+/// https://developer.mozilla.org/en-US/docs/Web/API/Blob
 const Blob = @This();
 
-pub fn init() Blob {
+/// Immutable slice of blob.
-    return .{};
+/// Note that another blob may hold a pointer/slice to this,
+/// so its better to leave the deallocation of it to arena allocator.
+slice: []const u8,
+/// MIME attached to blob. Can be an empty string.
+mime: []const u8,
+
+const InitOptions = struct {
+    /// MIME type.
+    type: []const u8 = "",
+    /// How to handle line endings (CR and LF).
+    /// `transparent` means do nothing, `native` expects CRLF (\r\n) on Windows.
+    endings: []const u8 = "transparent",
+};
+
+/// Creates a new Blob.
+pub fn init(
+    maybe_blob_parts: ?[]const []const u8,
+    maybe_options: ?InitOptions,
+    page: *Page,
+) !*Blob {
+    const options: InitOptions = maybe_options orelse .{};
+    // Setup MIME; This can be any string according to my observations.
+    const mime: []const u8 = blk: {
+        const t = options.type;
+        if (t.len == 0) {
+            break :blk "";
+        }
+
+        break :blk try page.arena.dupe(u8, t);
+    };
+
+    const slice = blk: {
+        if (maybe_blob_parts) |blob_parts| {
+            var w: Writer.Allocating = .init(page.arena);
+            const use_native_endings = std.mem.eql(u8, options.endings, "native");
+            try writeBlobParts(&w.writer, blob_parts, use_native_endings);
+
+            break :blk w.written();
+        }
+
+        break :blk "";
+    };
+
+    return page._factory.create(Blob{ .slice = slice, .mime = mime });
+}
+
+const largest_vector = @max(std.simd.suggestVectorLength(u8) orelse 1, 8);
+/// Array of possible vector sizes for the current arch in decrementing order.
+/// We may move this to some file for SIMD helpers in the future.
+const vector_sizes = blk: {
+    // Required for length calculation.
+    var n: usize = largest_vector;
+    var total: usize = 0;
+    while (n != 2) : (n /= 2) total += 1;
+    // Populate an array with vector sizes.
+    n = largest_vector;
+    var i: usize = 0;
+    var items: [total]usize = undefined;
+    while (n != 2) : (n /= 2) {
+        defer i += 1;
+        items[i] = n;
+    }
+
+    break :blk items;
+};
+
+/// Writes blob parts to given `Writer` with desired endings.
+fn writeBlobParts(
+    writer: *Writer,
+    blob_parts: []const []const u8,
+    use_native_endings: bool,
+) !void {
+    // Transparent.
+    if (!use_native_endings) {
+        for (blob_parts) |part| {
+            try writer.writeAll(part);
+        }
+
+        return;
+    }
+
+    // TODO: Windows support.
+
+    // Linux & Unix.
+    // Both Firefox and Chrome implement it as such:
+    // CRLF => LF
+    // CR   => LF
+    // So even though CR is not followed by LF, it gets replaced.
+    //
+    // I believe this is because such scenario is possible:
+    // ```
+    // let parts = [ "the quick\r", "\nbrown fox" ];
+    // ```
+    // In the example, one should have to check the part before in order to
+    // understand that CRLF is being presented in the final buffer.
+    // So they took a simpler approach, here's what given blob parts produce:
+    // ```
+    // "the quick\n\nbrown fox"
+    // ```
+    scan_parts: for (blob_parts) |part| {
+        var end: usize = 0;
+
+        inline for (vector_sizes) |vector_len| {
+            const Vec = @Vector(vector_len, u8);
+
+            while (end + vector_len <= part.len) : (end += vector_len) {
+                const cr: Vec = @splat('\r');
+                // Load chunk as vectors.
+                const slice = part[end..][0..vector_len];
+                const chunk: Vec = slice.*;
+                // Look for CR.
+                const match = chunk == cr;
+
+                // Create a bitset out of match vector.
+                const bitset = std.bit_set.IntegerBitSet(vector_len){
+                    .mask = @bitCast(@intFromBool(match)),
+                };
+
+                var iter = bitset.iterator(.{});
+                var relative_start: usize = 0;
+                while (iter.next()) |index| {
+                    _ = try writer.writeVec(&.{ slice[relative_start..index], "\n" });
+
+                    if (index + 1 != slice.len and slice[index + 1] == '\n') {
+                        relative_start = index + 2;
+                    } else {
+                        relative_start = index + 1;
+                    }
+                }
+
+                _ = try writer.writeVec(&.{slice[relative_start..]});
+            }
+        }
+
+        // Scalar scan fallback.
+        var relative_start: usize = end;
+        while (end < part.len) {
+            if (part[end] == '\r') {
+                _ = try writer.writeVec(&.{ part[relative_start..end], "\n" });
+
+                // Part ends with CR. We can continue to next part.
+                if (end + 1 == part.len) {
+                    continue :scan_parts;
+                }
+
+                // If next char is LF, skip it too.
+                if (part[end + 1] == '\n') {
+                    relative_start = end + 2;
+                } else {
+                    relative_start = end + 1;
+                }
+            }
+
+            end += 1;
+        }
+
+        // Write the remaining. We get this in such situations:
+        // `the quick brown\rfox`
+        // `the quick brown\r\nfox`
+        try writer.writeAll(part[relative_start..end]);
+    }
+}
+
+/// Returns a Promise that resolves with the contents of the blob
+/// as binary data contained in an ArrayBuffer.
+//pub fn arrayBuffer(self: *const Blob, page: *Page) !js.Promise {
+//    return page.js.resolvePromise(js.ArrayBuffer{ .values = self.slice });
+//}
+
+// TODO: Implement `stream`; requires `ReadableStream`.
+
+/// Returns a Promise that resolves with a string containing
+/// the contents of the blob, interpreted as UTF-8.
+pub fn text(self: *const Blob, page: *Page) !js.Promise {
+    return page.js.resolvePromise(self.slice);
+}
+
+/// Extension to Blob; works on Firefox and Safari.
+/// https://developer.mozilla.org/en-US/docs/Web/API/Blob/bytes
+/// Returns a Promise that resolves with a Uint8Array containing
+/// the contents of the blob as an array of bytes.
+pub fn bytes(self: *const Blob, page: *Page) !js.Promise {
+    return page.js.resolvePromise(js.TypedArray(u8){ .values = self.slice });
+}
+
+/// Returns a new Blob object which contains data
+/// from a subset of the blob on which it's called.
+pub fn getSlice(
+    self: *const Blob,
+    maybe_start: ?i32,
+    maybe_end: ?i32,
+    maybe_content_type: ?[]const u8,
+    page: *Page,
+) !Blob {
+    const mime: []const u8 = blk: {
+        if (maybe_content_type) |content_type| {
+            if (content_type.len == 0) {
+                break :blk "";
+            }
+
+            break :blk try page.arena.dupe(u8, content_type);
+        }
+
+        break :blk "";
+    };
+
+    const slice = self.slice;
+    if (maybe_start) |_start| {
+        const start = blk: {
+            if (_start < 0) {
+                break :blk slice.len -| @abs(_start);
+            }
+
+            break :blk @min(slice.len, @as(u31, @intCast(_start)));
+        };
+
+        const end: usize = blk: {
+            if (maybe_end) |_end| {
+                if (_end < 0) {
+                    break :blk @max(start, slice.len -| @abs(_end));
+                }
+
+                break :blk @min(slice.len, @max(start, @as(u31, @intCast(_end))));
+            }
+
+            break :blk slice.len;
+        };
+
+        return .{ .slice = slice[start..end], .mime = mime };
+    }
+
+    return .{ .slice = slice, .mime = mime };
+}
+
+/// Returns the size of the Blob in bytes.
+pub fn size(self: *const Blob) usize {
+    return self.slice.len;
+}
+
+/// Returns the type of Blob; likely a MIME type, yet anything can be given.
+pub fn @"type"(self: *const Blob) []const u8 {
+    return self.mime;
 }
 
 pub const JsApi = struct {
@@ -36,4 +281,9 @@ pub const JsApi = struct {
     };
 
     pub const constructor = bridge.constructor(Blob.init, .{});
+    pub const text = bridge.function(Blob.text, .{});
+    pub const bytes = bridge.function(Blob.bytes, .{});
+    pub const slice = bridge.function(Blob.getSlice, .{});
+    pub const size = bridge.accessor(Blob.size, null, .{});
+    pub const @"type" = bridge.accessor(Blob.type, null, .{});
 };