Implements writing delimited and length-prefixed sequence types #701

zslayton · 2024-01-31T13:46:41Z

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zslayton

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zslayton · 2024-01-31T13:52:22Z

src/lazy/encoder/binary/v1_0/writer.rs

-        let untyped_ptr: *mut () = ptr.cast();
-        untyped_ptr
-    }
-


🗺️ These methods were redundantly defined in two different modules, so I created a private unsafe_helpers module to house them.

zslayton · 2024-01-31T13:56:09Z

src/lazy/encoder/binary/v1_1/container_writers.rs

+    //      container.
+    //   2. a delimited container, this will be the parent's own encoding buffer, to which the delimited
+    //      container start opcode has already been written.
+    buffer: &'value mut BumpVec<'top, u8>,
 }

 impl<'value, 'top> BinaryContainerWriter_1_1<'value, 'top> {


🗺️ I did some refactoring of lifetimes that allowed me to remove some methods/types.

Previously, each container writer had two lifetime parameters and could instantiate an affiliated type with a single lifetime parameter to be used as a closure argument.

BinaryContainerWriter_1_1<'value, 'top> -> BinaryContainerValuesWriter_1_1<'value>

BinaryListWriter_1_1<'value, 'top> -> BinaryListValuesWriter_1_1<'value>

BinarySExpWriter_1_1<'value, 'top> -> BinarySExpValuesWriter_1_1<'value>

BinarStructWriter_1_1<'value, 'top> -> BinaryStructFieldsWriter_1_1<'value>

Now, the two-lifetime types can be used as the closure argument themselves which simplifies things quite a bit.

zslayton · 2024-01-31T14:01:38Z

src/lazy/encoder/binary/v1_1/value_writer.rs

@@ -24,6 +22,7 @@ use crate::{
 pub struct BinaryValueWriter_1_1<'value, 'top> {
    allocator: &'top BumpAllocator,
    encoding_buffer: &'value mut BumpVec<'top, u8>,
+    delimited_containers: bool,


🗺️ Where previously I was using type families to statically express different configurations (e.g. with/without annotations), I'm going to start moving towards branching on stored values.

zslayton · 2024-01-31T14:04:19Z

src/lazy/encoder/binary/v1_1/value_writer.rs

+    pub fn with_delimited_containers(mut self) -> Self {
+        self.delimited_containers = true;
+        self
+    }


🗺️ This builder-style config method allows users to write code like:

writer .value_writer() .with_delimited_containers() .write_sexp(|sexp| { for text in str_array { sexp.write_string(text)?; } })?;

If you start using delimited containers, and then you want to write a non-delimited container, how would you do that? E.g.: I want to write a struct where one field is a delimited list and another field is a length-prefixed list; or I want to write a delimited list that contains one or more length-prefixed s-expressions?

Each value gets its own ValueWriter; they're single-use. In your example, a value writer would be created for the outer struct, and another would be created for each of the nested field values, allowing you to configure the encoding options for each one separately.

or I want to write a delimited list that contains one or more length-prefixed s-expressions

writer .value_writer() .with_delimited_containers() .write_list(|list| { list // The type's `WriteAsIon` impl will use the default ValueWriter configuration (currently // always length-prefixed) .write([1, 2, 3].as_sexp())? // Also uses the default ValueWriter configuration (currently always length-prefixed) .write_sexp(|sexp| sexp.write(1)?.write(2)?.write(3)?)? // Allows you to explicitly configure the value writer .value_writer() .with_delimited_containers() .write([1, 2, 3].as_sexp())?; Ok(()) })?;

The above would produce a delimited list that contains two length-prefixed s-expressions and a delimited s-expression.

zslayton · 2024-01-31T14:05:48Z

src/lazy/encoder/binary/v1_1/value_writer.rs

    >(
        mut self,
        sexp_fn: F,
    ) -> IonResult<()> {
-        self.sexp_writer().write_values(sexp_fn)


🗺️ While it was very tempting to try and write a generic "sequence" implementation for the list/sexp impls to call, in practice I found that it required a lot of generics and ended up being not much shorter. I decided to just give each their own impl for simplicity.

This is just an idea, not a request for a change.
If you really want to DRY it up, I think it should work to do something like this:

fn write_length_prefixed_list< F: for<'a> FnOnce(&mut <Self as ValueWriter>::ListWriter<'a>) -> IonResult<()>, >( mut self, list_fn: F, ) -> IonResult<()> { const LIST_NIBBLE: u8 = 0xA; self.write_length_prefixed_sequence(LIST_NIBBLE, |container_writer| { // Create a BinaryListWriter_1_1 to pass to the user's closure. list_fn(&mut BinaryListWriter_1_1::new(container_writer)) }) } fn write_length_prefixed_sexp< F: for<'a> FnOnce(&mut <Self as ValueWriter>::SExpWriter<'a>) -> IonResult<()>, >( mut self, sexp_fn: F, ) -> IonResult<()> { const SEXP_NIBBLE: u8 = 0xB; self.write_length_prefixed_sequence(SEXP_NIBBLE, |container_writer| { // Create a BinarySExpWriter_1_1 to pass to the user's closure. sexp_fn(&mut BinarySExpWriter_1_1::new(container_writer)) }) } fn write_length_prefixed_sequence<F: FnOnce(BinaryContainerWriter_1_1) -> IonResult<()>>(mut self, container_nibble: u8, container_fn: F) -> IonResult<()> { // We're writing a length-prefixed sexp/list, so we need to set up a space to encode the list's children. let child_encoding_buffer = self .allocator .alloc_with(|| BumpVec::new_in(self.allocator)); let mut container_writer = BinaryContainerWriter_1_1::new(self.allocator, child_encoding_buffer); // Pass it to the closure, allowing the user to encode child values. container_fn(container_writer)?; // Write the appropriate opcode for a sexp of this length let encoded_length = container_writer.buffer().len(); match encoded_length { 0..=15 => { let opcode = (container_nibble << 4) | encoded_length as u8; self.push_byte(opcode); } _ => { let opcode = 0xF | container_nibble; // SExp or List w/FlexUInt length self.push_byte(opcode); FlexUInt::write_u64(self.encoding_buffer, encoded_length as u64)?; } } self.encoding_buffer .extend_from_slice(sexp_writer.container_writer.buffer()); Ok(()) }

zslayton · 2024-01-31T14:06:31Z

src/lazy/encoder/binary/v1_1/value_writer.rs

-    type StructWriter<'a> = BinaryStructFieldsWriter_1_1<'a>;
+    type ListWriter<'a> = BinaryListWriter_1_1<'value, 'top>;
+    type SExpWriter<'a> = BinarySExpWriter_1_1<'value, 'top>;
+    type StructWriter<'a> = BinaryStructWriter_1_1<'value, 'top>;


🗺️ The aforementioned change in closure argument types.

zslayton · 2024-01-31T14:07:38Z

src/lazy/encoder/binary/v1_1/writer.rs

-        let untyped_ptr: *mut () = ptr.cast();
-        untyped_ptr
-    }
-


🗺️ This is the second file where these methods were defined; they were removed and usages updated to use the unsafe_helpers module.

popematt · 2024-02-05T17:26:19Z

src/lazy/encoder/binary/v1_1/value_writer.rs

+    pub fn with_delimited_containers(mut self) -> Self {
+        self.delimited_containers = true;
+        self
+    }


If you start using delimited containers, and then you want to write a non-delimited container, how would you do that? E.g.: I want to write a struct where one field is a delimited list and another field is a length-prefixed list; or I want to write a delimited list that contains one or more length-prefixed s-expressions?

popematt · 2024-02-05T17:45:35Z

src/lazy/encoder/binary/v1_1/value_writer.rs

    >(
        mut self,
        sexp_fn: F,
    ) -> IonResult<()> {
-        self.sexp_writer().write_values(sexp_fn)


This is just an idea, not a request for a change.
If you really want to DRY it up, I think it should work to do something like this:

fn write_length_prefixed_list< F: for<'a> FnOnce(&mut <Self as ValueWriter>::ListWriter<'a>) -> IonResult<()>, >( mut self, list_fn: F, ) -> IonResult<()> { const LIST_NIBBLE: u8 = 0xA; self.write_length_prefixed_sequence(LIST_NIBBLE, |container_writer| { // Create a BinaryListWriter_1_1 to pass to the user's closure. list_fn(&mut BinaryListWriter_1_1::new(container_writer)) }) } fn write_length_prefixed_sexp< F: for<'a> FnOnce(&mut <Self as ValueWriter>::SExpWriter<'a>) -> IonResult<()>, >( mut self, sexp_fn: F, ) -> IonResult<()> { const SEXP_NIBBLE: u8 = 0xB; self.write_length_prefixed_sequence(SEXP_NIBBLE, |container_writer| { // Create a BinarySExpWriter_1_1 to pass to the user's closure. sexp_fn(&mut BinarySExpWriter_1_1::new(container_writer)) }) } fn write_length_prefixed_sequence<F: FnOnce(BinaryContainerWriter_1_1) -> IonResult<()>>(mut self, container_nibble: u8, container_fn: F) -> IonResult<()> { // We're writing a length-prefixed sexp/list, so we need to set up a space to encode the list's children. let child_encoding_buffer = self .allocator .alloc_with(|| BumpVec::new_in(self.allocator)); let mut container_writer = BinaryContainerWriter_1_1::new(self.allocator, child_encoding_buffer); // Pass it to the closure, allowing the user to encode child values. container_fn(container_writer)?; // Write the appropriate opcode for a sexp of this length let encoded_length = container_writer.buffer().len(); match encoded_length { 0..=15 => { let opcode = (container_nibble << 4) | encoded_length as u8; self.push_byte(opcode); } _ => { let opcode = 0xF | container_nibble; // SExp or List w/FlexUInt length self.push_byte(opcode); FlexUInt::write_u64(self.encoding_buffer, encoded_length as u64)?; } } self.encoding_buffer .extend_from_slice(sexp_writer.container_writer.buffer()); Ok(()) }

src/unsafe_helpers.rs

…ences

Zack Slayton added 8 commits January 16, 2024 15:43

Implements writing v1.1 decimals

c840b0c

improved comments

213a4e5

Implements writing short-form timestamps

2f47b10

Merge remote-tracking branch 'origin/main' into write-timestamp

759027f

fixed comment typo

d307368

Implements writing long-form v1.1 timestamps

49ca57d

Implements writing delimited and length-prefixed sequence types

f50e183

clippy suggestions

9bc075a

zslayton commented Jan 31, 2024

View reviewed changes

zslayton requested review from popematt and tgregg January 31, 2024 14:07

This was referenced Jan 31, 2024

Binary write support for delimited containers #703

Closed

Binary write support for length-prefixed containers #705

Closed

popematt reviewed Feb 5, 2024

View reviewed changes

Zack Slayton added 4 commits February 7, 2024 11:43

Incorporates review feedback

4e0e1d7

Merge remote-tracking branch 'origin/main' into write-timestamp

845a6d8

Merge remote-tracking branch 'origin/write-timestamp' into write-sequ…

e6b998d

…ences

Adds more doc comments to the unsafe_helpers module

ac01abc

zslayton requested a review from popematt February 7, 2024 17:49

tgregg approved these changes Feb 7, 2024

View reviewed changes

Base automatically changed from write-timestamp to main February 8, 2024 14:06

Merge remote-tracking branch 'origin/main' into write-sequences

1359198

zslayton merged commit cac2784 into main Feb 8, 2024
20 checks passed

zslayton deleted the write-sequences branch February 8, 2024 14:38

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Implements writing delimited and length-prefixed sequence types #701

Implements writing delimited and length-prefixed sequence types #701

zslayton commented Jan 31, 2024

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Implements writing delimited and length-prefixed sequence types #701

Implements writing delimited and length-prefixed sequence types #701

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