Add file reader (#1155)

* Add file reader
* Add a simple test example of parsing settings.
* Use new FileLineReader to parse Glass presets
* Trim CRLF from Glass preset name

firmware/application/file_reader.hpp

@@ -0,0 +1,155 @@
+/*
+ * Copyright (C) 2023 Kyle Reed
+ *
+ * This file is part of PortaPack.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __FILE_READER_HPP__
+#define __FILE_READER_HPP__
+
+#include "file.hpp"
+#include <cstring>
+#include <cstdlib>
+#include <string>
+#include <string_view>
+#include <vector>
+
+/* BufferType requires the following members
+ * Size size()
+ * Result<Size> read(void* data, Size bytes_to_read)
+ * Result<Offset> seek(uint32_t offset)
+ */
+
+/* Iterates lines in buffer split on '\n'.
+ * NB: very basic iterator impl, don't try anything fancy with it. */
+template <typename BufferType>
+class BufferLineReader {
+   public:
+    struct iterator {
+        bool operator!=(const iterator& other) {
+            return this->pos_ != other.pos_ || this->reader_ != other.reader_;
+        }
+
+        const std::string& operator*() {
+            if (!cached_) {
+                bool ok = reader_->read_line(*this);
+                cached_ = true;
+
+                if (!ok) *this = reader_->end();
+            }
+
+            return line_data_;
+        }
+
+        iterator& operator++() {
+            const auto size = reader_->size();
+
+            if (pos_ < size) {
+                cached_ = false;
+                pos_ += line_data_.length();
+            }
+
+            if (pos_ >= size)
+                *this = reader_->end();
+
+            return *this;
+        }
+
+        typename BufferType::Size pos_{};
+        BufferLineReader* reader_{};
+        bool cached_ = false;
+        std::string line_data_{};
+    };
+
+    BufferLineReader(BufferType& buffer)
+        : buffer_{buffer} {}
+
+    iterator begin() { return {0, this}; }
+    iterator end() { return {size(), this}; }
+
+    typename BufferType::Size size() const { return buffer_.size(); }
+
+   private:
+    BufferType& buffer_;
+
+    bool read_line(iterator& it) {
+        constexpr size_t buf_size = 0x80;
+        char buf[buf_size];
+        uint32_t offset = 0;
+
+        it.line_data_.resize(buf_size);
+        buffer_.seek(it.pos_);
+
+        while (true) {
+            auto read = buffer_.read(buf, buf_size);
+            if (!read)
+                return false;
+
+            // Find newline.
+            auto len = 0u;
+            for (; len < *read; ++len) {
+                if (buf[len] == '\n') {
+                    ++len;
+                    break;
+                }
+            }
+
+            // Reallocate if needed.
+            if (offset + len >= it.line_data_.length())
+                it.line_data_.resize(offset + len);
+
+            std::strncpy(&it.line_data_[offset], buf, len);
+            offset += len;
+
+            if (len < buf_size)
+                break;
+        }
+
+        it.line_data_.resize(offset);
+        return true;
+    }
+};
+
+using FileLineReader = BufferLineReader<File>;
+
+/* Splits the string on the specified char and returns
+ * a vector of string_views. NB: the lifetime of the
+ * string to split must be maintained while the views
+ * are used or they will dangle. */
+std::vector<std::string_view> split_string(std::string_view str, char c) {
+    std::vector<std::string_view> cols;
+    size_t start = 0;
+
+    while (start < str.length()) {
+        auto it = str.find(c, start);
+
+        if (it == str.npos)
+            break;
+
+        // TODO: allow empty?
+        cols.emplace_back(&str[start], it - start);
+        start = it + 1;
+    }
+
+    if (start <= str.length() && !str.empty())
+        cols.emplace_back(&str[start], str.length() - start);
+
+    return cols;
+}
+
+#endif