More work on format

.bazelrc

@@ -15,3 +15,5 @@ build --cxxopt=-Wno-unused-macros
 build --cxxopt=-Wno-documentation-unknown-command
 build --cxxopt=-Wno-extra-semi-stmt
 build --cxxopt=-Wno-extra-semi
+
+test --test_output=errors

asl/format.cpp

@@ -7,6 +7,63 @@ void asl::format_internals::format(
     int64_t arg_count)
 {
     formatter f(writer);
-    
+
-    f.write("Hello", 5);
+
+    int64_t arg = 0;
+
+    const char* begin = fmt;
+    while (*fmt != '\0')
+    {
+        if (fmt[0] == '{')
+        {
+            if (fmt[1] == '}')
+            {
+                if (arg < arg_count)
+                {
+                    f.write(begin, fmt - begin);
+                    fmt += 2;
+                    begin = fmt;
+
+                    args[arg].fn(f, args[arg].data);
+                    arg += 1;
+                }
+                else
+                {
+                    f.write(begin, fmt - begin);
+                    fmt += 2;
+                    begin = fmt;
+
+                    f.write("<ERROR>", 7);
+                }
+            }
+            else if (fmt[1] == '{')
+            {
+                fmt += 1;
+                f.write(begin, fmt - begin);
+                fmt += 1;
+                begin = fmt;
+            }
+            else
+            {
+                f.write(begin, fmt - begin);
+                fmt += 1;
+                begin = fmt;
+
+                f.write("<ERROR>", 7);
+            }
+        }
+        else if (fmt[0] == '}' && fmt[1] == '}')
+        {
+            fmt += 1;
+            f.write(begin, fmt - begin);
+            fmt += 1;
+            begin = fmt;
+        }
+        else
+        {
+            fmt += 1;
+        }
+    }
+
+    f.write(begin, fmt - begin);
 }

asl/format.hpp

@@ -51,7 +51,7 @@ struct type_erased_arg
 // @Todo Use span
 void format(writer*, const char* fmt, const type_erased_arg* args, int64_t arg_count);
 
-} // internals
+} // namespace internals
 
 class formatter
 {
@@ -73,7 +73,7 @@ public:
 template<typename... Args>
 void format(writer* w, const char* fmt, const Args&... args)
 {
-    auto type_erased_args[] = {
+    format_internals::type_erased_arg type_erased_args[] = {
         format_internals::type_erased_arg(args)...
     };
 
@@ -81,4 +81,16 @@ void format(writer* w, const char* fmt, const Args&... args)
     format_internals::format(w, fmt, type_erased_args, types_count<Args...>);
 }
 
+// @Todo Use string_view
+inline void format(writer* w, const char* fmt)
+{
+    format_internals::format(w, fmt, nullptr, 0);
+}
+
+template<int64_t N>
+void AslFormat(formatter& f, const char (&str)[N])
+{
+    f.write(str, N - 1);
+}
+
 } // namespace asl

asl/format_tests.cpp

@@ -0,0 +1,82 @@
+#include "asl/format.hpp"
+
+#include <cstdlib>
+#include <cstring>
+#include <cassert>
+#include <cstdio>
+
+// @Todo Improve this to use our utilities, not the C stdlib
+
+static_assert(asl::formattable<decltype("Hello")>);
+
+class StringSink : public asl::writer
+{
+    int64_t m_current_len{};
+    char*   m_data{};
+    
+public:
+    void write(const char* str, int64_t len) override
+    {
+        m_data = (char*)realloc(m_data, (size_t)(m_current_len + len + 1));
+        memcpy(m_data + m_current_len, str, (size_t)len);
+        m_current_len += len;
+        m_data[m_current_len] = '\0';
+    }
+
+    constexpr const char* cstr() const { return m_data; }
+
+    void reset()
+    {
+        m_current_len = 0;
+        free(m_data);
+        m_data = nullptr;
+    }
+};
+
+int main()
+{
+    StringSink sink;
+
+    // @Todo Use the testing framework
+
+    asl::format(&sink, "Hello, world!");
+    assert(strcmp(sink.cstr(), "Hello, world!") == 0);
+
+    sink.reset();
+    asl::format(&sink, "");
+    assert(strcmp(sink.cstr(), "") == 0);
+
+    sink.reset();
+    asl::format(&sink, "Hello, {}!", "world");
+    assert(strcmp(sink.cstr(), "Hello, world!") == 0);
+
+    sink.reset();
+    asl::format(&sink, "Hello, {}! {}", "world");
+    assert(strcmp(sink.cstr(), "Hello, world! <ERROR>") == 0);
+
+    sink.reset();
+    asl::format(&sink, "Hello, pup!", "world");
+    assert(strcmp(sink.cstr(), "Hello, pup!") == 0);
+
+    sink.reset();
+    asl::format(&sink, "{}", "CHEESE");
+    assert(strcmp(sink.cstr(), "CHEESE") == 0);
+
+    sink.reset();
+    asl::format(&sink, "{   ", "CHEESE");
+    assert(strcmp(sink.cstr(), "<ERROR>   ") == 0);
+
+    sink.reset();
+    asl::format(&sink, "{", "CHEESE");
+    assert(strcmp(sink.cstr(), "<ERROR>") == 0);
+
+    sink.reset();
+    asl::format(&sink, "a{{b");
+    assert(strcmp(sink.cstr(), "a{b") == 0);
+
+    sink.reset();
+    asl::format(&sink, "{{{}}} }", "CHEESE");
+    assert(strcmp(sink.cstr(), "{CHEESE} }") == 0);
+
+    return 0;
+}