Introduce dropsection

README.md

@@ -45,6 +45,10 @@ Can be set to allow or prohibit unlisted additional exports.
 The following presets are provided:
 - `ewasm`: Verifies that the `main` function and `memory` is exported. Disallows any unlisted exports.
 
+### dropsection
+
+Removes selected sections from the module.
+
 ### deployer
 
 Wraps module into an ewasm-compatible constructor. It has two presets:

libchisel/src/dropsection.rs

@@ -0,0 +1,166 @@
+use super::{ModuleError, ModuleTranslator};
+
+use parity_wasm::builder::*;
+use parity_wasm::elements::*;
+
+/// Enum on which ModuleTranslator is implemented.
+pub enum DropSection<'a> {
+    NamesSection,
+    /// Name of the custom section.
+    CustomSectionByName(&'a String),
+    /// Index of the custom section.
+    CustomSectionByIndex(usize),
+    /// Index of the unknown section.
+    UnknownSectionByIndex(usize),
+}
+
+fn names_section_index_for(module: &Module) -> Option<usize> {
+    module.sections().iter().position(|e| match e {
+        Section::Name(_) => true,
+        _ => false,
+    })
+}
+
+fn custom_section_index_for(module: &Module, name: &String) -> Option<usize> {
+    module.sections().iter().position(|e| match e {
+        Section::Custom(_section) => _section.name() == name,
+        _ => false,
+    })
+}
+
+impl<'a> DropSection<'a> {
+    fn find_index(&self, module: &Module) -> Option<usize> {
+        match &self {
+            DropSection::NamesSection => names_section_index_for(module),
+            DropSection::CustomSectionByName(name) => custom_section_index_for(module, &name),
+            DropSection::CustomSectionByIndex(index) => Some(*index),
+            DropSection::UnknownSectionByIndex(index) => Some(*index),
+        }
+    }
+
+    fn drop_section(&self, module: &mut Module) -> Result<bool, ModuleError> {
+        let index = self.find_index(&module);
+        if index.is_none() {
+            return Ok(false);
+        }
+        let index = index.unwrap();
+
+        let sections = module.sections_mut();
+        if index >= sections.len() {
+            return Ok(false);
+        }
+        sections.remove(index);
+
+        Ok(true)
+    }
+}
+
+impl<'a> ModuleTranslator for DropSection<'a> {
+    fn translate_inplace(&self, module: &mut Module) -> Result<bool, ModuleError> {
+        Ok(self.drop_section(module)?)
+    }
+
+    fn translate(&self, module: &Module) -> Result<Option<Module>, ModuleError> {
+        let mut ret = module.clone();
+        if self.drop_section(&mut ret)? {
+            Ok(Some(ret))
+        } else {
+            Ok(None)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use parity_wasm::builder;
+
+    #[test]
+    fn keep_intact() {
+        let mut module = builder::module().build();
+        let name = "empty".to_string();
+        let dropper = DropSection::CustomSectionByName(&name);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, false);
+    }
+
+    #[test]
+    fn keep_intact_custom_section() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let name = "empty".to_string();
+        let dropper = DropSection::CustomSectionByName(&name);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, false);
+    }
+
+    #[test]
+    fn remove_custom_section() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let name = "test".to_string();
+        let dropper = DropSection::CustomSectionByName(&name);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, true);
+    }
+
+    #[test]
+    fn remove_custom_section_by_index() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let dropper = DropSection::CustomSectionByIndex(0);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, true);
+    }
+
+    #[test]
+    fn remove_oob_custom_section_by_index() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let dropper = DropSection::CustomSectionByIndex(1);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, false);
+    }
+
+    #[test]
+    fn remove_custom_unknown_by_index() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let dropper = DropSection::UnknownSectionByIndex(0);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, true);
+    }
+
+    #[test]
+    fn remove_oob_unknown_section_by_index() {
+        let mut module = builder::module()
+            .with_section(Section::Custom(CustomSection::new(
+                "test".to_string(),
+                vec![],
+            )))
+            .build();
+        let dropper = DropSection::UnknownSectionByIndex(1);
+        let did_change = dropper.translate_inplace(&mut module).unwrap();
+        assert_eq!(did_change, false);
+    }
+}

libchisel/src/lib.rs

@@ -8,6 +8,7 @@ pub mod imports;
 
 pub mod checkstartfunc;
 pub mod deployer;
+pub mod dropsection;
 pub mod remapimports;
 pub mod remapstart;
 pub mod repack;