Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/exr/src/meta/mod.rs

@@ -0,0 +1,821 @@
+
+//! Describes all meta data possible in an exr file.
+//! Contains functionality to read and write meta data from bytes.
+//! Browse the `exr::image` module to get started with the high-level interface.
+
+pub mod attribute;
+pub mod header;
+
+
+use crate::io::*;
+use ::smallvec::SmallVec;
+use self::attribute::*;
+use crate::block::chunk::{TileCoordinates, CompressedBlock};
+use crate::error::*;
+use std::fs::File;
+use std::io::{BufReader};
+use crate::math::*;
+use std::collections::{HashSet};
+use std::convert::TryFrom;
+use crate::meta::header::{Header};
+use crate::block::{BlockIndex, UncompressedBlock};
+
+
+// TODO rename MetaData to ImageInfo?
+
+/// Contains the complete meta data of an exr image.
+/// Defines how the image is split up in the file,
+/// the number and type of images and channels,
+/// and various other attributes.
+/// The usage of custom attributes is encouraged.
+#[derive(Debug, Clone, PartialEq)]
+pub struct MetaData {
+
+    /// Some flags summarizing the features that must be supported to decode the file.
+    pub requirements: Requirements,
+
+    /// One header to describe each layer in this file.
+    // TODO rename to layer descriptions?
+    pub headers: Headers,
+}
+
+
+/// List of `Header`s.
+pub type Headers = SmallVec<[Header; 3]>;
+
+/// List of `OffsetTable`s.
+pub type OffsetTables = SmallVec<[OffsetTable; 3]>;
+
+
+/// The offset table is an ordered list of indices referencing pixel data in the exr file.
+/// For each pixel tile in the image, an index exists, which points to the byte-location
+/// of the corresponding pixel data in the file. That index can be used to load specific
+/// portions of an image without processing all bytes in a file. For each header,
+/// an offset table exists with its indices ordered by `LineOrder::Increasing`.
+// If the multipart bit is unset and the chunkCount attribute is not present,
+// the number of entries in the chunk table is computed using the
+// dataWindow, tileDesc, and compression attribute.
+//
+// If the multipart bit is set, the header must contain a
+// chunkCount attribute, that contains the length of the offset table.
+pub type OffsetTable = Vec<u64>;
+
+
+/// A summary of requirements that must be met to read this exr file.
+/// Used to determine whether this file can be read by a given reader.
+/// It includes the OpenEXR version number. This library aims to support version `2.0`.
+#[derive(Clone, Copy, Eq, PartialEq, Debug, Hash)]
+pub struct Requirements {
+
+    /// This library supports reading version 1 and 2, and writing version 2.
+    // TODO write version 1 for simple images
+    pub file_format_version: u8,
+
+    /// If true, this image has tiled blocks and contains only a single layer.
+    /// If false and not deep and not multilayer, this image is a single layer image with scan line blocks.
+    pub is_single_layer_and_tiled: bool,
+
+    // in c or bad c++ this might have been relevant (omg is he allowed to say that)
+    /// Whether this file has strings with a length greater than 31.
+    /// Strings can never be longer than 255.
+    pub has_long_names: bool,
+
+    /// This image contains at least one layer with deep data.
+    pub has_deep_data: bool,
+
+    /// Whether this file contains multiple layers.
+    pub has_multiple_layers: bool,
+}
+
+
+/// Locates a rectangular section of pixels in an image.
+#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
+pub struct TileIndices {
+
+    /// Index of the tile.
+    pub location: TileCoordinates,
+
+    /// Pixel size of the tile.
+    pub size: Vec2<usize>,
+}
+
+/// How the image pixels are split up into separate blocks.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum BlockDescription {
+
+    /// The image is divided into scan line blocks.
+    /// The number of scan lines in a block depends on the compression method.
+    ScanLines,
+
+    /// The image is divided into tile blocks.
+    /// Also specifies the size of each tile in the image
+    /// and whether this image contains multiple resolution levels.
+    Tiles(TileDescription)
+}
+
+
+/*impl TileIndices {
+    pub fn cmp(&self, other: &Self) -> Ordering {
+        match self.location.level_index.1.cmp(&other.location.level_index.1) {
+            Ordering::Equal => {
+                match self.location.level_index.0.cmp(&other.location.level_index.0) {
+                    Ordering::Equal => {
+                        match self.location.tile_index.1.cmp(&other.location.tile_index.1) {
+                            Ordering::Equal => {
+                                self.location.tile_index.0.cmp(&other.location.tile_index.0)
+                            },
+
+                            other => other,
+                        }
+                    },
+
+                    other => other
+                }
+            },
+
+            other => other
+        }
+    }
+}*/
+
+impl BlockDescription {
+
+    /// Whether this image is tiled. If false, this image is divided into scan line blocks.
+    pub fn has_tiles(&self) -> bool {
+        match self {
+            BlockDescription::Tiles { .. } => true,
+            _ => false
+        }
+    }
+}
+
+
+
+
+
+/// The first four bytes of each exr file.
+/// Used to abort reading non-exr files.
+pub mod magic_number {
+    use super::*;
+
+    /// The first four bytes of each exr file.
+    pub const BYTES: [u8; 4] = [0x76, 0x2f, 0x31, 0x01];
+
+    /// Without validation, write this instance to the byte stream.
+    pub fn write(write: &mut impl Write) -> Result<()> {
+        u8::write_slice(write, &self::BYTES)
+    }
+
+    /// Consumes four bytes from the reader and returns whether the file may be an exr file.
+    // TODO check if exr before allocating BufRead
+    pub fn is_exr(read: &mut impl Read) -> Result<bool> {
+        let mut magic_num = [0; 4];
+        u8::read_slice(read, &mut magic_num)?;
+        Ok(magic_num == self::BYTES)
+    }
+
+    /// Validate this image. If it is an exr file, return `Ok(())`.
+    pub fn validate_exr(read: &mut impl Read) -> UnitResult {
+        if self::is_exr(read)? {
+            Ok(())
+
+        } else {
+            Err(Error::invalid("file identifier missing"))
+        }
+    }
+}
+
+/// A `0_u8` at the end of a sequence.
+pub mod sequence_end {
+    use super::*;
+
+    /// Number of bytes this would consume in an exr file.
+    pub fn byte_size() -> usize {
+        1
+    }
+
+    /// Without validation, write this instance to the byte stream.
+    pub fn write<W: Write>(write: &mut W) -> UnitResult {
+        0_u8.write(write)
+    }
+
+    /// Peeks the next byte. If it is zero, consumes the byte and returns true.
+    pub fn has_come(read: &mut PeekRead<impl Read>) -> Result<bool> {
+        Ok(read.skip_if_eq(0)?)
+    }
+}
+
+fn missing_attribute(name: &str) -> Error {
+    Error::invalid(format!("missing or invalid {} attribute", name))
+}
+
+
+/// Compute the number of tiles required to contain all values.
+pub fn compute_block_count(full_res: usize, tile_size: usize) -> usize {
+    // round up, because if the image is not evenly divisible by the tiles,
+    // we add another tile at the end (which is only partially used)
+    RoundingMode::Up.divide(full_res, tile_size)
+}
+
+/// Compute the start position and size of a block inside a dimension.
+#[inline]
+pub fn calculate_block_position_and_size(total_size: usize, block_size: usize, block_index: usize) -> Result<(usize, usize)> {
+    let block_position = block_size * block_index;
+
+    Ok((
+        block_position,
+        calculate_block_size(total_size, block_size, block_position)?
+    ))
+}
+
+/// Calculate the size of a single block. If this is the last block,
+/// this only returns the required size, which is always smaller than the default block size.
+// TODO use this method everywhere instead of convoluted formulas
+#[inline]
+pub fn calculate_block_size(total_size: usize, block_size: usize, block_position: usize) -> Result<usize> {
+    if block_position >= total_size {
+        return Err(Error::invalid("block index"))
+    }
+
+    if block_position + block_size <= total_size {
+        Ok(block_size)
+    }
+    else {
+        Ok(total_size - block_position)
+    }
+}
+
+
+/// Calculate number of mip levels in a given resolution.
+// TODO this should be cached? log2 may be very expensive
+pub fn compute_level_count(round: RoundingMode, full_res: usize) -> usize {
+    usize::try_from(round.log2(u32::try_from(full_res).unwrap())).unwrap() + 1
+}
+
+/// Calculate the size of a single mip level by index.
+// TODO this should be cached? log2 may be very expensive
+pub fn compute_level_size(round: RoundingMode, full_res: usize, level_index: usize) -> usize {
+    assert!(level_index < std::mem::size_of::<usize>() * 8, "largest level size exceeds maximum integer value");
+    round.divide(full_res,  1 << level_index).max(1)
+}
+
+/// Iterates over all rip map level resolutions of a given size, including the indices of each level.
+/// The order of iteration conforms to `LineOrder::Increasing`.
+// TODO cache these?
+// TODO compute these directly instead of summing up an iterator?
+pub fn rip_map_levels(round: RoundingMode, max_resolution: Vec2<usize>) -> impl Iterator<Item=(Vec2<usize>, Vec2<usize>)> {
+    rip_map_indices(round, max_resolution).map(move |level_indices|{
+        // TODO progressively divide instead??
+        let width = compute_level_size(round, max_resolution.width(), level_indices.x());
+        let height = compute_level_size(round, max_resolution.height(), level_indices.y());
+        (level_indices, Vec2(width, height))
+    })
+}
+
+/// Iterates over all mip map level resolutions of a given size, including the indices of each level.
+/// The order of iteration conforms to `LineOrder::Increasing`.
+// TODO cache all these level values when computing table offset size??
+// TODO compute these directly instead of summing up an iterator?
+pub fn mip_map_levels(round: RoundingMode, max_resolution: Vec2<usize>) -> impl Iterator<Item=(usize, Vec2<usize>)> {
+    mip_map_indices(round, max_resolution)
+        .map(move |level_index|{
+            // TODO progressively divide instead??
+            let width = compute_level_size(round, max_resolution.width(), level_index);
+            let height = compute_level_size(round, max_resolution.height(), level_index);
+            (level_index, Vec2(width, height))
+        })
+}
+
+/// Iterates over all rip map level indices of a given size.
+/// The order of iteration conforms to `LineOrder::Increasing`.
+pub fn rip_map_indices(round: RoundingMode, max_resolution: Vec2<usize>) -> impl Iterator<Item=Vec2<usize>> {
+    let (width, height) = (
+        compute_level_count(round, max_resolution.width()),
+        compute_level_count(round, max_resolution.height())
+    );
+
+    (0..height).flat_map(move |y_level|{
+        (0..width).map(move |x_level|{
+            Vec2(x_level, y_level)
+        })
+    })
+}
+
+/// Iterates over all mip map level indices of a given size.
+/// The order of iteration conforms to `LineOrder::Increasing`.
+pub fn mip_map_indices(round: RoundingMode, max_resolution: Vec2<usize>) -> impl Iterator<Item=usize> {
+    0..compute_level_count(round, max_resolution.width().max(max_resolution.height()))
+}
+
+/// Compute the number of chunks that an image is divided into. May be an expensive operation.
+// If not multilayer and chunkCount not present,
+// the number of entries in the chunk table is computed
+// using the dataWindow and tileDesc attributes and the compression format
+pub fn compute_chunk_count(compression: Compression, data_size: Vec2<usize>, blocks: BlockDescription) -> usize {
+
+    if let BlockDescription::Tiles(tiles) = blocks {
+        let round = tiles.rounding_mode;
+        let Vec2(tile_width, tile_height) = tiles.tile_size;
+
+        // TODO cache all these level values??
+        use crate::meta::attribute::LevelMode::*;
+        match tiles.level_mode {
+            Singular => {
+                let tiles_x = compute_block_count(data_size.width(), tile_width);
+                let tiles_y = compute_block_count(data_size.height(), tile_height);
+                tiles_x * tiles_y
+            }
+
+            MipMap => {
+                mip_map_levels(round, data_size).map(|(_, Vec2(level_width, level_height))| {
+                    compute_block_count(level_width, tile_width) * compute_block_count(level_height, tile_height)
+                }).sum()
+            },
+
+            RipMap => {
+                rip_map_levels(round, data_size).map(|(_, Vec2(level_width, level_height))| {
+                    compute_block_count(level_width, tile_width) * compute_block_count(level_height, tile_height)
+                }).sum()
+            }
+        }
+    }
+
+    // scan line blocks never have mip maps
+    else {
+        compute_block_count(data_size.height(), compression.scan_lines_per_block())
+    }
+}
+
+
+
+impl MetaData {
+
+    /// Read the exr meta data from a file.
+    /// Use `read_from_unbuffered` instead if you do not have a file.
+    /// Does not validate the meta data.
+    #[must_use]
+    pub fn read_from_file(path: impl AsRef<::std::path::Path>, pedantic: bool) -> Result<Self> {
+        Self::read_from_unbuffered(File::open(path)?, pedantic)
+    }
+
+    /// Buffer the reader and then read the exr meta data from it.
+    /// Use `read_from_buffered` if your reader is an in-memory reader.
+    /// Use `read_from_file` if you have a file path.
+    /// Does not validate the meta data.
+    #[must_use]
+    pub fn read_from_unbuffered(unbuffered: impl Read, pedantic: bool) -> Result<Self> {
+        Self::read_from_buffered(BufReader::new(unbuffered), pedantic)
+    }
+
+    /// Read the exr meta data from a reader.
+    /// Use `read_from_file` if you have a file path.
+    /// Use `read_from_unbuffered` if this is not an in-memory reader.
+    /// Does not validate the meta data.
+    #[must_use]
+    pub fn read_from_buffered(buffered: impl Read, pedantic: bool) -> Result<Self> {
+        let mut read = PeekRead::new(buffered);
+        MetaData::read_unvalidated_from_buffered_peekable(&mut read, pedantic)
+    }
+
+    /// Does __not validate__ the meta data completely.
+    #[must_use]
+    pub(crate) fn read_unvalidated_from_buffered_peekable(read: &mut PeekRead<impl Read>, pedantic: bool) -> Result<Self> {
+        magic_number::validate_exr(read)?;
+
+        let requirements = Requirements::read(read)?;
+
+        // do this check now in order to fast-fail for newer versions and features than version 2
+        requirements.validate()?;
+
+        let headers = Header::read_all(read, &requirements, pedantic)?;
+
+        // TODO check if supporting requirements 2 always implies supporting requirements 1
+        Ok(MetaData { requirements, headers })
+    }
+
+    /// Validates the meta data.
+    #[must_use]
+    pub(crate) fn read_validated_from_buffered_peekable(
+        read: &mut PeekRead<impl Read>, pedantic: bool
+    ) -> Result<Self> {
+        let meta_data = Self::read_unvalidated_from_buffered_peekable(read, !pedantic)?;
+        MetaData::validate(meta_data.headers.as_slice(), pedantic)?;
+        Ok(meta_data)
+    }
+
+    /// Validates the meta data and writes it to the stream.
+    /// If pedantic, throws errors for files that may produce errors in other exr readers.
+    /// Returns the automatically detected minimum requirement flags.
+    pub(crate) fn write_validating_to_buffered(write: &mut impl Write, headers: &[Header], pedantic: bool) -> Result<Requirements> {
+        // pedantic validation to not allow slightly invalid files
+        // that still could be read correctly in theory
+        let minimal_requirements = Self::validate(headers, pedantic)?;
+
+        magic_number::write(write)?;
+        minimal_requirements.write(write)?;
+        Header::write_all(headers, write, minimal_requirements.has_multiple_layers)?;
+        Ok(minimal_requirements)
+    }
+
+    /// Read one offset table from the reader for each header.
+    pub fn read_offset_tables(read: &mut PeekRead<impl Read>, headers: &Headers) -> Result<OffsetTables> {
+        headers.iter()
+            .map(|header| u64::read_vec(read, header.chunk_count, u16::MAX as usize, None, "offset table size"))
+            .collect()
+    }
+
+    /// Skip the offset tables by advancing the reader by the required byte count.
+    // TODO use seek for large (probably all) tables!
+    pub fn skip_offset_tables(read: &mut PeekRead<impl Read>, headers: &Headers) -> Result<usize> {
+        let chunk_count: usize = headers.iter().map(|header| header.chunk_count).sum();
+        crate::io::skip_bytes(read, chunk_count * u64::BYTE_SIZE)?; // TODO this should seek for large tables
+        Ok(chunk_count)
+    }
+
+    /// This iterator tells you the block indices of all blocks that must be in the image.
+    /// The order of the blocks depends on the `LineOrder` attribute
+    /// (unspecified line order is treated the same as increasing line order).
+    /// The blocks written to the file must be exactly in this order,
+    /// except for when the `LineOrder` is unspecified.
+    /// The index represents the block index, in increasing line order, within the header.
+    pub fn enumerate_ordered_header_block_indices(&self) -> impl '_ + Iterator<Item=(usize, BlockIndex)> {
+        crate::block::enumerate_ordered_header_block_indices(&self.headers)
+    }
+
+    /// Go through all the block indices in the correct order and call the specified closure for each of these blocks.
+    /// That way, the blocks indices are filled with real block data and returned as an iterator.
+    /// The closure returns the an `UncompressedBlock` for each block index.
+    pub fn collect_ordered_blocks<'s>(&'s self, mut get_block: impl 's + FnMut(BlockIndex) -> UncompressedBlock)
+        -> impl 's + Iterator<Item=(usize, UncompressedBlock)>
+    {
+        self.enumerate_ordered_header_block_indices().map(move |(index_in_header, block_index)|{
+            (index_in_header, get_block(block_index))
+        })
+    }
+
+    /// Go through all the block indices in the correct order and call the specified closure for each of these blocks.
+    /// That way, the blocks indices are filled with real block data and returned as an iterator.
+    /// The closure returns the byte data for each block index.
+    pub fn collect_ordered_block_data<'s>(&'s self, mut get_block_data: impl 's + FnMut(BlockIndex) -> Vec<u8>)
+        -> impl 's + Iterator<Item=(usize, UncompressedBlock)>
+    {
+        self.collect_ordered_blocks(move |block_index|
+            UncompressedBlock { index: block_index, data: get_block_data(block_index) }
+        )
+    }
+
+    /// Validates this meta data. Returns the minimal possible requirements.
+    pub fn validate(headers: &[Header], pedantic: bool) -> Result<Requirements> {
+        if headers.len() == 0 {
+            return Err(Error::invalid("at least one layer is required"));
+        }
+
+        let deep = false; // TODO deep data
+        let is_multilayer = headers.len() > 1;
+        let first_header_has_tiles = headers.iter().next()
+            .map_or(false, |header| header.blocks.has_tiles());
+
+        let mut minimal_requirements = Requirements {
+            // according to the spec, version 2  should only be necessary if `is_multilayer || deep`.
+            // but the current open exr library does not support images with version 1, so always use version 2.
+            file_format_version: 2,
+
+            // start as low as possible, later increasing if required
+            has_long_names: false,
+
+            is_single_layer_and_tiled: !is_multilayer && first_header_has_tiles,
+            has_multiple_layers: is_multilayer,
+            has_deep_data: deep,
+        };
+
+        for header in headers {
+            if header.deep { // TODO deep data (and then remove this check)
+                return Err(Error::unsupported("deep data not supported yet"));
+            }
+
+            header.validate(is_multilayer, &mut minimal_requirements.has_long_names, pedantic)?;
+        }
+
+        // TODO validation fn!
+        /*if let Some(max) = max_pixel_bytes {
+            let byte_size: usize = headers.iter()
+                .map(|header| header.total_pixel_bytes())
+                .sum();
+
+            if byte_size > max {
+                return Err(Error::invalid("image larger than specified maximum"));
+            }
+        }*/
+
+        if pedantic { // check for duplicate header names
+            let mut header_names = HashSet::with_capacity(headers.len());
+            for header in headers {
+                if !header_names.insert(&header.own_attributes.layer_name) {
+                    return Err(Error::invalid(format!(
+                        "duplicate layer name: `{}`",
+                        header.own_attributes.layer_name.as_ref().expect("header validation bug")
+                    )));
+                }
+            }
+        }
+
+        if pedantic {
+            let must_share = headers.iter().flat_map(|header| header.own_attributes.other.iter())
+                .any(|(_, value)| value.to_chromaticities().is_ok() || value.to_time_code().is_ok());
+
+            if must_share {
+                return Err(Error::invalid("chromaticities and time code attributes must must not exist in own attributes but shared instead"));
+            }
+        }
+
+        if pedantic && headers.len() > 1 { // check for attributes that should not differ in between headers
+            let first_header = headers.first().expect("header count validation bug");
+            let first_header_attributes = &first_header.shared_attributes;
+
+            for header in &headers[1..] {
+                if &header.shared_attributes != first_header_attributes {
+                    return Err(Error::invalid("display window, pixel aspect, chromaticities, and time code attributes must be equal for all headers"))
+                }
+            }
+        }
+
+        debug_assert!(minimal_requirements.validate().is_ok(), "inferred requirements are invalid");
+        Ok(minimal_requirements)
+    }
+}
+
+
+
+
+impl Requirements {
+
+    // this is actually used for control flow, as the number of headers may be 1 in a multilayer file
+    /// Is this file declared to contain multiple layers?
+    pub fn is_multilayer(&self) -> bool {
+        self.has_multiple_layers
+    }
+
+    /// Read the value without validating.
+    pub fn read<R: Read>(read: &mut R) -> Result<Self> {
+        use ::bit_field::BitField;
+
+        let version_and_flags = u32::read(read)?;
+
+        // take the 8 least significant bits, they contain the file format version number
+        let version = (version_and_flags & 0x000F) as u8;
+
+        // the 24 most significant bits are treated as a set of boolean flags
+        let is_single_tile = version_and_flags.get_bit(9);
+        let has_long_names = version_and_flags.get_bit(10);
+        let has_deep_data = version_and_flags.get_bit(11);
+        let has_multiple_layers = version_and_flags.get_bit(12);
+
+        // all remaining bits except 9, 10, 11 and 12 are reserved and should be 0
+        // if a file has any of these bits set to 1, it means this file contains
+        // a feature that we don't support
+        let unknown_flags = version_and_flags >> 13; // all flags excluding the 12 bits we already parsed
+
+        if unknown_flags != 0 { // TODO test if this correctly detects unsupported files
+            return Err(Error::unsupported("too new file feature flags"));
+        }
+
+        let version = Requirements {
+            file_format_version: version,
+            is_single_layer_and_tiled: is_single_tile, has_long_names,
+            has_deep_data, has_multiple_layers,
+        };
+
+        Ok(version)
+    }
+
+    /// Without validation, write this instance to the byte stream.
+    pub fn write<W: Write>(self, write: &mut W) -> UnitResult {
+        use ::bit_field::BitField;
+
+        // the 8 least significant bits contain the file format version number
+        // and the flags are set to 0
+        let mut version_and_flags = self.file_format_version as u32;
+
+        // the 24 most significant bits are treated as a set of boolean flags
+        version_and_flags.set_bit(9, self.is_single_layer_and_tiled);
+        version_and_flags.set_bit(10, self.has_long_names);
+        version_and_flags.set_bit(11, self.has_deep_data);
+        version_and_flags.set_bit(12, self.has_multiple_layers);
+        // all remaining bits except 9, 10, 11 and 12 are reserved and should be 0
+
+        version_and_flags.write(write)?;
+        Ok(())
+    }
+
+    /// Validate this instance.
+    pub fn validate(&self) -> UnitResult {
+        if self.file_format_version == 2 {
+
+            match (
+                self.is_single_layer_and_tiled, self.has_deep_data, self.has_multiple_layers,
+                self.file_format_version
+            ) {
+                // Single-part scan line. One normal scan line image.
+                (false, false, false, 1..=2) => Ok(()),
+
+                // Single-part tile. One normal tiled image.
+                (true, false, false, 1..=2) => Ok(()),
+
+                // Multi-part (new in 2.0).
+                // Multiple normal images (scan line and/or tiled).
+                (false, false, true, 2) => Ok(()),
+
+                // Single-part deep data (new in 2.0).
+                // One deep tile or deep scan line part
+                (false, true, false, 2) => Ok(()),
+
+                // Multi-part deep data (new in 2.0).
+                // Multiple parts (any combination of:
+                // tiles, scan lines, deep tiles and/or deep scan lines).
+                (false, true, true, 2) => Ok(()),
+
+                _ => Err(Error::invalid("file feature flags"))
+            }
+        }
+        else {
+            Err(Error::unsupported("file versions other than 2.0 are not supported"))
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::meta::header::{ImageAttributes, LayerAttributes};
+
+    #[test]
+    fn round_trip_requirements() {
+        let requirements = Requirements {
+            file_format_version: 2,
+            is_single_layer_and_tiled: true,
+            has_long_names: false,
+            has_deep_data: true,
+            has_multiple_layers: false
+        };
+
+        let mut data: Vec<u8> = Vec::new();
+        requirements.write(&mut data).unwrap();
+        let read = Requirements::read(&mut data.as_slice()).unwrap();
+        assert_eq!(requirements, read);
+    }
+
+    #[test]
+    fn round_trip(){
+        let header = Header {
+            channels: ChannelList::new(smallvec![
+                    ChannelDescription {
+                        name: Text::from("main"),
+                        sample_type: SampleType::U32,
+                        quantize_linearly: false,
+                        sampling: Vec2(1, 1)
+                    }
+                ],
+            ),
+            compression: Compression::Uncompressed,
+            line_order: LineOrder::Increasing,
+            deep_data_version: Some(1),
+            chunk_count: compute_chunk_count(Compression::Uncompressed, Vec2(2000, 333), BlockDescription::ScanLines),
+            max_samples_per_pixel: Some(4),
+            shared_attributes: ImageAttributes {
+                pixel_aspect: 3.0,
+                .. ImageAttributes::new(IntegerBounds {
+                    position: Vec2(2,1),
+                    size: Vec2(11, 9)
+                })
+            },
+
+            blocks: BlockDescription::ScanLines,
+            deep: false,
+            layer_size: Vec2(2000, 333),
+            own_attributes: LayerAttributes {
+                layer_name: Some(Text::from("test name lol")),
+                layer_position: Vec2(3, -5),
+                screen_window_center: Vec2(0.3, 99.0),
+                screen_window_width: 0.19,
+                .. Default::default()
+            }
+        };
+
+        let meta = MetaData {
+            requirements: Requirements {
+                file_format_version: 2,
+                is_single_layer_and_tiled: false,
+                has_long_names: false,
+                has_deep_data: false,
+                has_multiple_layers: false
+            },
+            headers: smallvec![ header ],
+        };
+
+
+        let mut data: Vec<u8> = Vec::new();
+        MetaData::write_validating_to_buffered(&mut data, meta.headers.as_slice(), true).unwrap();
+        let meta2 = MetaData::read_from_buffered(data.as_slice(), false).unwrap();
+        MetaData::validate(meta2.headers.as_slice(), true).unwrap();
+        assert_eq!(meta, meta2);
+    }
+
+    #[test]
+    fn infer_low_requirements() {
+        let header_version_1_short_names = Header {
+            channels: ChannelList::new(smallvec![
+                    ChannelDescription {
+                        name: Text::from("main"),
+                        sample_type: SampleType::U32,
+                        quantize_linearly: false,
+                        sampling: Vec2(1, 1)
+                    }
+                ],
+            ),
+            compression: Compression::Uncompressed,
+            line_order: LineOrder::Increasing,
+            deep_data_version: Some(1),
+            chunk_count: compute_chunk_count(Compression::Uncompressed, Vec2(2000, 333), BlockDescription::ScanLines),
+            max_samples_per_pixel: Some(4),
+            shared_attributes: ImageAttributes {
+                pixel_aspect: 3.0,
+                .. ImageAttributes::new(IntegerBounds {
+                    position: Vec2(2,1),
+                    size: Vec2(11, 9)
+                })
+            },
+            blocks: BlockDescription::ScanLines,
+            deep: false,
+            layer_size: Vec2(2000, 333),
+            own_attributes: LayerAttributes {
+                other: vec![
+                    (Text::try_from("x").unwrap(), AttributeValue::F32(3.0)),
+                    (Text::try_from("y").unwrap(), AttributeValue::F32(-1.0)),
+                ].into_iter().collect(),
+                .. Default::default()
+            }
+        };
+
+        let low_requirements = MetaData::validate(
+            &[header_version_1_short_names], true
+        ).unwrap();
+
+        assert_eq!(low_requirements.has_long_names, false);
+        assert_eq!(low_requirements.file_format_version, 2); // always have version 2
+        assert_eq!(low_requirements.has_deep_data, false);
+        assert_eq!(low_requirements.has_multiple_layers, false);
+    }
+
+    #[test]
+    fn infer_high_requirements() {
+        let header_version_2_long_names = Header {
+            channels: ChannelList::new(
+                smallvec![
+                    ChannelDescription {
+                        name: Text::new_or_panic("main"),
+                        sample_type: SampleType::U32,
+                        quantize_linearly: false,
+                        sampling: Vec2(1, 1)
+                    }
+                ],
+            ),
+            compression: Compression::Uncompressed,
+            line_order: LineOrder::Increasing,
+            deep_data_version: Some(1),
+            chunk_count: compute_chunk_count(Compression::Uncompressed, Vec2(2000, 333), BlockDescription::ScanLines),
+            max_samples_per_pixel: Some(4),
+            shared_attributes: ImageAttributes {
+                pixel_aspect: 3.0,
+                .. ImageAttributes::new(IntegerBounds {
+                    position: Vec2(2,1),
+                    size: Vec2(11, 9)
+                })
+            },
+            blocks: BlockDescription::ScanLines,
+            deep: false,
+            layer_size: Vec2(2000, 333),
+            own_attributes: LayerAttributes {
+                layer_name: Some(Text::new_or_panic("oasdasoidfj")),
+                other: vec![
+                    (Text::new_or_panic("xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"), AttributeValue::F32(3.0)),
+                    (Text::new_or_panic("y"), AttributeValue::F32(-1.0)),
+                ].into_iter().collect(),
+                .. Default::default()
+            }
+        };
+
+        let mut layer_2 = header_version_2_long_names.clone();
+        layer_2.own_attributes.layer_name = Some(Text::new_or_panic("anythingelse"));
+
+        let low_requirements = MetaData::validate(
+            &[header_version_2_long_names, layer_2], true
+        ).unwrap();
+
+        assert_eq!(low_requirements.has_long_names, true);
+        assert_eq!(low_requirements.file_format_version, 2);
+        assert_eq!(low_requirements.has_deep_data, false);
+        assert_eq!(low_requirements.has_multiple_layers, true);
+    }
+}
+