json: Replace line_reader.rs symlink with a copy for now

Windows doesn't handle symlinks very well.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/issues/166

text/json/src/line_reader.rs

@@ -1 +0,0 @@
-../../../video/closedcaption/src/line_reader.rs

text/json/src/line_reader.rs

@@ -0,0 +1,333 @@
+// Copyright (C) 2018 Sebastian Dröge <sebastian@centricular.com>
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Library General Public
+// License as published by the Free Software Foundation; either
+// version 2 of the License, or (at your option) any later version.
+//
+// This library 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
+// Library General Public License for more details.
+//
+// You should have received a copy of the GNU Library General Public
+// License along with this library; if not, write to the
+// Free Software Foundation, Inc., 51 Franklin Street, Suite 500,
+// Boston, MA 02110-1335, USA.
+
+use std::collections::VecDeque;
+
+#[derive(Debug)]
+pub struct LineReader<T: AsRef<[u8]>> {
+    queue: VecDeque<T>,
+    // Read position into the queue in bytes
+    read_pos: usize,
+    // Offset into queue where we have to look for a newline
+    // All previous items don't contain a newline
+    search_pos: usize,
+    buf: Vec<u8>,
+}
+
+impl<T: AsRef<[u8]>> LineReader<T> {
+    pub fn new() -> LineReader<T> {
+        Self {
+            queue: VecDeque::new(),
+            read_pos: 0,
+            search_pos: 0,
+            buf: Vec::new(),
+        }
+    }
+
+    pub fn push(&mut self, b: T) {
+        self.queue.push_back(b);
+    }
+
+    /// Drops everything from the internal queue that was previously returned, i.e.
+    /// if previously a line was returned we drop this whole line so that we can
+    /// proceed with the next line
+    fn drop_previous_line(&mut self) {
+        // Drop everything we read the last time now
+        while self.read_pos > 0
+            && self.read_pos >= self.queue.front().map(|f| f.as_ref().len()).unwrap_or(0)
+        {
+            self.read_pos -= self.queue.front().map(|f| f.as_ref().len()).unwrap_or(0);
+            self.queue.pop_front();
+            if self.search_pos > 0 {
+                self.search_pos -= 1;
+            }
+        }
+
+        self.buf.clear();
+    }
+
+    #[allow(unused)]
+    pub fn line_or_drain(&mut self) -> Option<&[u8]> {
+        self.line_with_drain(true)
+    }
+
+    #[allow(unused)]
+    pub fn line(&mut self) -> Option<&[u8]> {
+        self.line_with_drain(false)
+    }
+
+    /// Searches the first '\n' in the currently queued buffers and returns the index in buffers
+    /// inside the queue and the index in bytes from the beginning of the queue, or None.
+    ///
+    /// Also updates the search_pos so that we don't look again in the previous buffers on the next
+    /// call
+    fn find_newline(&mut self) -> Option<(usize, usize)> {
+        let mut offset = 0;
+        for (idx, buf) in self.queue.iter().enumerate() {
+            let buf = buf.as_ref();
+
+            // Fast skip-ahead
+            if idx < self.search_pos {
+                offset += buf.len();
+                continue;
+            }
+
+            let pos = buf
+                .iter()
+                .enumerate()
+                .skip(if idx == 0 { self.read_pos } else { 0 })
+                .find(|(_, b)| **b == b'\n')
+                .map(|(idx, _)| idx);
+
+            if let Some(pos) = pos {
+                // On the next call we have to search in this buffer again
+                // as it might contain a second newline
+                self.search_pos = idx;
+                return Some((idx, offset + pos + 1));
+            }
+
+            // This buffer did not contain a newline so we don't have to look
+            // in it again next time
+            self.search_pos = idx + 1;
+            offset += buf.len();
+        }
+
+        None
+    }
+
+    /// Copies length bytes from all buffers from the beginning until last_idx into our internal
+    /// buffer, and skips the first offset bytes from the first buffer.
+    fn copy_into_internal_buffer(&mut self, last_idx: usize, offset: usize, len: usize) {
+        // Reserve space for the whole line beforehand
+        if self.buf.capacity() < len {
+            self.buf.reserve(len - self.buf.capacity());
+        }
+
+        // Then iterate over all buffers inside the queue until the one that contains
+        // the newline character
+        for (idx, buf) in self.queue.iter().enumerate().take(last_idx + 1) {
+            let buf = buf.as_ref();
+
+            // Calculate how much data we still have to copy
+            let rem = len - self.buf.len();
+            assert!(rem > 0);
+
+            // For the first index we need to take into account the offset. The first
+            // bytes might have to be skipped and as such we have fewer bytes available
+            // than the whole length of the buffer
+            let buf_len = if idx == 0 {
+                assert!(offset < buf.len());
+                buf.len() - offset
+            } else {
+                buf.len()
+            };
+
+            // Calculate how much we can copy from this buffer. At most the size of the buffer
+            // itself, but never more than the amount we still have to copy overall
+            let copy_len = if rem > buf_len { buf_len } else { rem };
+            assert!(copy_len > 0);
+
+            if idx == 0 {
+                self.buf
+                    .extend_from_slice(&buf[offset..(offset + copy_len)]);
+            } else {
+                self.buf.extend_from_slice(&buf[..copy_len]);
+            }
+        }
+
+        assert_eq!(self.buf.len(), len);
+    }
+
+    pub fn line_with_drain(&mut self, drain: bool) -> Option<&[u8]> {
+        // Drop all data from the previous line
+        self.drop_previous_line();
+
+        // read_pos must always be inside the first buffer of our queue here
+        // or otherwise we went into an inconsistent state: the first buffer(s)
+        // would've had to be dropped above then as they are not relevant anymore
+        assert!(
+            self.read_pos == 0
+                || self.read_pos < self.queue.front().map(|f| f.as_ref().len()).unwrap_or(0)
+        );
+
+        // Find the next newline character from our previous position
+        if let Some((idx, pos)) = self.find_newline() {
+            // We now need to copy everything from the old read_pos to the new
+            // pos, and on the next call we have to start from the new pos
+            let old_read_pos = self.read_pos;
+            self.read_pos = pos;
+
+            assert!(self.read_pos > old_read_pos);
+            assert!(idx < self.queue.len());
+
+            // If the newline is found in the first buffer in our queue, we can directly return
+            // the slice from it without doing any copying.
+            //
+            // On average this should be the most common case.
+            if idx == 0 {
+                let buf = self.queue.front().unwrap().as_ref();
+                return Some(&buf[old_read_pos..self.read_pos]);
+            } else {
+                // Copy into our internal buffer as the current line spans multiple buffers
+                let len = self.read_pos - old_read_pos;
+                self.copy_into_internal_buffer(idx, old_read_pos, len);
+
+                return Some(&self.buf[0..len]);
+            }
+        }
+
+        // No newline found above and we're not draining, so let's wait until
+        // more data is available that might contain a newline character
+        if !drain {
+            return None;
+        }
+
+        if self.queue.is_empty() {
+            return None;
+        }
+
+        // When draining and we only have a single buffer in the queue we can
+        // directly return a slice into it
+        if self.queue.len() == 1 {
+            let res = &self.queue.front().unwrap().as_ref()[self.read_pos..];
+            self.read_pos += res.len();
+            self.search_pos = 1;
+            return Some(res);
+        }
+
+        // Otherwise we have to copy everything that is remaining into our
+        // internal buffer and then return a slice from that
+        let len = self.queue.iter().map(|v| v.as_ref().len()).sum();
+        if self.buf.capacity() < len {
+            self.buf.reserve(len - self.buf.capacity());
+        }
+
+        for (idx, ref v) in self.queue.iter().enumerate() {
+            if idx == 0 {
+                self.buf.extend_from_slice(&v.as_ref()[self.read_pos..]);
+            } else {
+                self.buf.extend_from_slice(v.as_ref());
+            }
+        }
+
+        self.read_pos += self.buf.len();
+        self.search_pos = self.queue.len();
+
+        Some(self.buf.as_ref())
+    }
+
+    pub fn clear(&mut self) {
+        self.queue.clear();
+        self.read_pos = 0;
+        self.search_pos = 0;
+        self.buf.clear();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::LineReader;
+
+    #[test]
+    fn test_single_buffer() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nefgh\nijkl\n".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), Some(b"ijkl\n".as_ref()));
+        assert_eq!(r.line(), None);
+    }
+
+    #[test]
+    fn test_empty_line() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nefgh\n\nijkl\n".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), Some(b"\n".as_ref()));
+        assert_eq!(r.line(), Some(b"ijkl\n".as_ref()));
+        assert_eq!(r.line(), None);
+    }
+
+    #[test]
+    fn test_multi_buffer_split() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nef".as_ref()));
+        r.push(Vec::from(b"gh\nijkl\n".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), Some(b"ijkl\n".as_ref()));
+        assert_eq!(r.line(), None);
+    }
+
+    #[test]
+    fn test_multi_buffer_split_2() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\ne".as_ref()));
+        r.push(Vec::from(b"f".as_ref()));
+        r.push(Vec::from(b"g".as_ref()));
+        r.push(Vec::from(b"h\nijkl\n".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), Some(b"ijkl\n".as_ref()));
+        assert_eq!(r.line(), None);
+    }
+
+    #[test]
+    fn test_single_buffer_drain() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nefgh\nijkl".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), None);
+        assert_eq!(r.line_or_drain(), Some(b"ijkl".as_ref()));
+        assert_eq!(r.line_or_drain(), None);
+    }
+
+    #[test]
+    fn test_single_buffer_drain_multi_line() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nefgh\n".as_ref()));
+        r.push(Vec::from(b"ijkl".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), None);
+        assert_eq!(r.line_or_drain(), Some(b"ijkl".as_ref()));
+        assert_eq!(r.line_or_drain(), None);
+    }
+
+    #[test]
+    fn test_single_buffer_drain_multi_line_2() {
+        let mut r = LineReader::new();
+        r.push(Vec::from(b"abcd\nefgh\ni".as_ref()));
+        r.push(Vec::from(b"j".as_ref()));
+        r.push(Vec::from(b"k".as_ref()));
+        r.push(Vec::from(b"l".as_ref()));
+
+        assert_eq!(r.line(), Some(b"abcd\n".as_ref()));
+        assert_eq!(r.line(), Some(b"efgh\n".as_ref()));
+        assert_eq!(r.line(), None);
+        assert_eq!(r.line_or_drain(), Some(b"ijkl".as_ref()));
+        assert_eq!(r.line_or_drain(), None);
+    }
+}