From f6912acdbd546c021412fb79f26da7f61ea2d9a8 Mon Sep 17 00:00:00 2001
From: Dzmitry Malyshau <kvarkus@gmail.com>
Date: Tue, 18 Feb 2020 17:27:12 -0500
Subject: [PATCH] Add parsing states

---
 src/lib.rs   |   2 +-
 src/parse.rs | 140 ++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 123 insertions(+), 19 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 9165bec25e..ec39a4bf6c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,7 @@ pub mod msl;
 mod parse;
 mod storage;
 
-pub use parse::{parse, parse_u8_slice, ParseError};
+pub use parse::{Parser, ParseError, parse_u8_slice};
 
 use crate::storage::{Storage, Token};
 
diff --git a/src/parse.rs b/src/parse.rs
index 08e482c180..77ed9d798f 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -3,27 +3,131 @@ use crate::storage::Storage;
 #[derive(Debug)]
 pub enum ParseError {
     InvalidHeader,
+    InvalidWordCount,
+    UnexpectedInstruction(ModuleState, spirv::Op),
     UnknownInstruction,
+    InvalidOperandCount(spirv::Op, u16),
     IncompleteData,
 }
 
-pub fn parse(mut data: impl Iterator<Item = u32>) -> Result<super::Module, ParseError> {
-    let header = {
-        if data.next().ok_or(ParseError::IncompleteData)? != spirv::MAGIC_NUMBER {
-            return Err(ParseError::InvalidHeader);
+struct Instruction {
+    op: spirv::Op,
+    wc: u16,
+}
+
+impl Instruction {
+    fn expect(&self, count: u16) -> Result<(), ParseError> {
+        if self.wc == count {
+            Ok(())
+        } else {
+            Err(ParseError::InvalidOperandCount(self.op, self.wc))
         }
-        let version_raw = data.next().ok_or(ParseError::IncompleteData)?.to_le_bytes();
-        super::Header {
-            version: (version_raw[2], version_raw[1], version_raw[0]),
-            generator: 0,
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
+pub enum ModuleState {
+    Empty,
+    Capability,
+    Extension,
+    ExtInstImport,
+    MemoryModel,
+    EntryPoint,
+    ExecutionMode,
+    Source,
+    Name,
+    ModuleProcessed,
+    Annotation,
+    Type,
+    FunctionDecl,
+    FunctionDef,
+}
+
+pub struct Parser<I> {
+    data: I,
+    state: ModuleState,
+}
+
+impl<I: Iterator<Item = u32>> Parser<I> {
+    pub fn new(data: I) -> Self {
+        Parser {
+            data,
+            state: ModuleState::Empty,
         }
-    };
-    Ok(super::Module {
-        header,
-        struct_declarations: Storage::new(),
-        functions: Storage::new(),
-        entry_points: Vec::new(),
-    })
+    }
+
+    fn next(&mut self) -> Result<u32, ParseError> {
+        self.data.next().ok_or(ParseError::IncompleteData)
+    }
+
+    fn next_inst(&mut self) -> Result<Instruction, ParseError> {
+        const LAST_KNOWN_OPCODE: spirv::Op = spirv::Op::MemberDecorateStringGOOGLE;
+
+        let word = self.next()?;
+        let (wc, opcode) = ((word >> 16) as u16, (word & 0xffff) as u16);
+        if wc == 0 {
+            return Err(ParseError::InvalidWordCount);
+        }
+        if opcode > LAST_KNOWN_OPCODE as u16 {
+            return Err(ParseError::UnknownInstruction);
+        }
+
+        Ok(Instruction {
+            op: unsafe {
+                std::mem::transmute(opcode as u32)
+            },
+            wc,
+        })
+    }
+
+    fn switch(&mut self, state: ModuleState, inst: &Instruction, word_count: u16) -> Result<(), ParseError> {
+        if state < self.state {
+            return Err(ParseError::UnexpectedInstruction(self.state, inst.op))
+        } else {
+            self.state = state;
+            inst.expect(word_count)
+        }
+    }
+
+    pub fn parse(&mut self) -> Result<super::Module, ParseError> {
+        let header = {
+            if self.next()? != spirv::MAGIC_NUMBER {
+                return Err(ParseError::InvalidHeader);
+            }
+            let version_raw = self.next()?.to_le_bytes();
+            let generator = self.next()?;
+            let _bound = self.next()?;
+            let _schema = self.next()?;
+            super::Header {
+                version: (version_raw[2], version_raw[1], version_raw[0]),
+                generator,
+            }
+        };
+
+        while let Ok(inst) = self.next_inst() {
+            use spirv::Op;
+            match inst.op {
+                Op::Capability => {
+                    self.switch(ModuleState::Capability, &inst, 2)?;
+                    let _capability = self.next()?;
+                }
+                Op::MemoryModel => {
+                    self.switch(ModuleState::MemoryModel, &inst, 3)?;
+                    let _addressing_model = self.next()?;
+                    let _memory_model = self.next()?;
+                },
+                _ => return Err(ParseError::UnexpectedInstruction(self.state, inst.op))
+                //TODO
+            }
+        }
+
+        Ok(super::Module {
+            header,
+            struct_declarations: Storage::new(),
+            functions: Storage::new(),
+            entry_points: Vec::new(),
+        })
+    }
 }
 
 pub fn parse_u8_slice(data: &[u8]) -> Result<super::Module, ParseError> {
@@ -33,10 +137,10 @@ pub fn parse_u8_slice(data: &[u8]) -> Result<super::Module, ParseError> {
         return Err(ParseError::IncompleteData);
     }
 
-    parse(data
+    let words = data
         .chunks(4)
-        .map(|c| u32::from_le_bytes(c.try_into().unwrap()))
-    )
+        .map(|c| u32::from_le_bytes(c.try_into().unwrap()));
+    Parser::new(words).parse()
 }
 
 #[cfg(test)]