From 23ed9e610a6b33024b20a7826ef79681cdaf24a8 Mon Sep 17 00:00:00 2001
From: Robin Voetter <robin@voetter.nl>
Date: Mon, 14 Oct 2019 01:58:45 +0200
Subject: [PATCH] XML unescape iterator

---
 build.zig         |  16 +++---
 generator/xml.zig | 121 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 131 insertions(+), 6 deletions(-)
 create mode 100644 generator/xml.zig

diff --git a/build.zig b/build.zig
index 0f9d7c8..3c0173a 100644
--- a/build.zig
+++ b/build.zig
@@ -1,14 +1,18 @@
-const Builder = @import("std").build.Builder;
+const std = @import("std");
+const Builder = std.build.Builder;
 
 pub fn build(b: *Builder) void {
-    const exe = b.addExecutable("vulkan-zig-gen", "generator/main.zig");
-    exe.setBuildMode(b.standardReleaseOptions());
+    const generator = b.addExecutable("vulkan-zig-gen", "generator/main.zig");
+    generator.setBuildMode(b.standardReleaseOptions());
 
-    const run_cmd = exe.run();
+    var test_step = b.step("test", "Run all the tests");
+    test_step.dependOn(&b.addTest("generator/xml.zig").step);
+
+    const run_cmd = generator.run();
 
     const run_step = b.step("run", "");
     run_step.dependOn(&run_cmd.step);
 
-    b.default_step.dependOn(&exe.step);
-    b.installArtifact(exe);
+    b.default_step.dependOn(&generator.step);
+    b.installArtifact(generator);
 }
diff --git a/generator/xml.zig b/generator/xml.zig
new file mode 100644
index 0000000..e293320
--- /dev/null
+++ b/generator/xml.zig
@@ -0,0 +1,121 @@
+const std = @import("std");
+const unicode = std.unicode;
+const testing = std.testing;
+const InStream = std.io.InStream;
+
+pub const Text = struct {
+    pub raw: []const u8,
+
+    pub fn iter_unescaped(self: *Text) UnescapeIterator {
+        return UnescapeIterator{
+            .raw = self.raw,
+            .i = 0
+        };
+    }
+};
+
+pub const UnescapeIterator = struct{
+    raw: []const u8,
+    i: usize,
+
+    pub fn init(raw: []const u8) UnescapeIterator {
+        return UnescapeIterator {
+            .raw = raw,
+            .i = 0
+        };
+    }
+
+    fn nextCodepoint(self: *UnescapeIterator) !?u32 {
+        if (self.i >= self.raw.len) {
+            return null;
+        }
+
+        const cp_len = try unicode.utf8ByteSequenceLength(self.raw[self.i]);
+        if (cp_len + self.i > self.raw.len) {
+            return error.InvalidUtf8;
+        }
+
+        const cp = try unicode.utf8Decode(self.raw[self.i .. self.i + cp_len]);
+        self.i += cp_len;
+        return cp;
+    }
+
+    fn unescape(self: *UnescapeIterator) !u32 {
+        var entity: [5]u8 = undefined;
+
+        var offset: usize = 0;
+        while (try self.nextCodepoint()) |cp| {
+            entity[offset] = std.math.cast(u8, cp) catch return error.InvalidEntity;
+            if (cp == ';') {
+                break;
+            }
+
+            offset += 1;
+            if (offset == entity.len) {
+                return error.InvalidEntity;
+            }
+        } else {
+            return error.InvalidEntity;
+        }
+
+        if (std.mem.startsWith(u8, entity, "lt;")) {
+            return '<';
+        } else if (std.mem.startsWith(u8, entity, "gt;")) {
+            return '>';
+        } else if (std.mem.startsWith(u8, entity, "amp;")) {
+            return '&';
+        } else if (std.mem.startsWith(u8, entity, "apos;")) {
+            return '\'';
+        } else if (std.mem.startsWith(u8, entity, "quot;")) {
+            return '"';
+        } else {
+            return error.InvalidEntity;
+        }
+    }
+
+    pub fn next(self: *UnescapeIterator) !?u32 {
+        const cp = (try self.nextCodepoint()) orelse return null;
+
+        if (cp == '&') {
+            return try self.unescape();
+        } else {
+            return cp;
+        }
+    }
+};
+
+fn testUnescapeIterator(text: []const u8, expected: []const u8) !void {
+    var it = UnescapeIterator.init(text);
+    var i: usize = 0;
+    defer testing.expect(i == expected.len);
+
+    while (try it.next()) |cp| {
+        testing.expect(cp == expected[i]);
+        i += 1;
+    }
+}
+
+test "unescape iterator" {
+    try testUnescapeIterator("simpleabc", "simpleabc");
+    try testUnescapeIterator("a&lt;b&amp;c&gt;d&quot;e&apos;f&lt;", "a<b&c>d\"e'f<");
+    testing.expectError(error.InvalidEntity, testUnescapeIterator("oof&&", "oof"));
+    testing.expectError(error.InvalidEntity, testUnescapeIterator("oof&test;", "oof"));
+    testing.expectError(error.InvalidEntity, testUnescapeIterator("oof&pythons", "oof"));
+}
+
+pub const Event = union(enum) {
+    open_tag,
+    close_tag,
+    attribute,
+    text,
+};
+
+pub const Parser = struct {
+    source: []const u8,
+
+    pub fn init(source: []const u8) Parser {
+        return Parser{
+            .source = source
+        };
+    }
+};