clean up path logic a bit

1 files changed, 47 insertions, 0 deletions

diff --git a/lib/nes/common/path-builder.cc b/lib/nes/common/path-builder.cc
new file mode 100644
index 0000000..67190dc
--- /dev/null
+++ b/lib/nes/common/path-builder.cc
@@ -0,0 +1,47 @@
+#include "nes/common/path-builder.hh"
+
+namespace nes
+{
+	path_builder::path_builder(char* buffer, u32 const buffer_length)
+		: buffer_{ buffer }
+		, buffer_length_{ buffer_length }
+	{
+		// Initialize the path to "/" if possible.
+		if (buffer_length > 0) { buffer_[actual_length_++] = '/'; }
+	}
+
+	auto path_builder::push(std::string_view component) -> bool
+	{
+		// Trim leading and trailing slashes
+		while (!component.empty() && component[0] == '/') { component = component.substr(1); }
+		while (!component.empty() && component[component.length() - 1] == '/') { component = component.substr(0, component.length() - 1); }
+		if (component.empty() || std::find(component.begin(), component.end(), '/') != component.end()) { return false; }
+
+		// Check if there is enough remaining capacity for "/<component>"
+		auto const add_leading_slash = actual_length_ == 0 || buffer_[actual_length_ - 1] != '/';
+		auto const length = component.length() + (add_leading_slash ? 1 : 0);
+		if (actual_length_ + length > buffer_length_) { return false; }
+
+		// Append "/<component>"
+		if (add_leading_slash) { buffer_[actual_length_++] = '/'; }
+		for (auto i = u32{ 0 }; i < component.length(); ++i) { buffer_[actual_length_++] = component[i]; }
+
+		return true;
+	}
+
+	auto path_builder::pop() -> bool
+	{
+		if (actual_length_ == 0 || buffer_[actual_length_ - 1] == '/') { return false; }
+
+		// Find the start of the last component.
+		auto last_start = actual_length_ - 1;
+		while (last_start > 0 && buffer_[last_start] != '/') { last_start -= 1; }
+
+		// Drop the slash if we are not at the root.
+		if (last_start == 0) { last_start += 1; }
+
+		// Drop everything including the trailing slash.
+		actual_length_ = last_start;
+		return true;
+	}
+} // namespace nes
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