Remove std and core features (#137)

This commit performs a similar transformation as
bytecodealliance/wasmtime#554, with similar motivation listed out there
as well.

Cargo.toml

@@ -11,27 +11,14 @@ A simple event-driven library for parsing WebAssembly binary files.
 exclude = ["fuzz/**/*", "tests/**/*", "testsuite/**/*"]
 edition = "2018"
 
-[dependencies]
-
 [dev-dependencies]
 criterion = "0.2"
 wast = "3.0.4"
 
-[dependencies.hashbrown]
-version = "0.5.0"
-optional = true
-
 [badges]
 travis-ci = { repository = "yurydelendik/wasmparser.rs" }
 
 [features]
-# The "std" feature enables use of libstd. The "core" feature enables use
-# of some minimal std-like replacement libraries. At least one of these two
-# features needs to be enabled.
-default = ["std"]
-std = []
-core = ["hashbrown"]
-
 # The "deterministic" feature supports only wasm code with "deterministic" execution
 # across any hardware. This feature is very critical for many Blockchain infrastructures
 # that rely on deterministic executions of smart contracts across different hardwares.

src/binary_reader.rs

@@ -938,7 +938,7 @@ impl<'a> BinaryReader<'a> {
         } else {
             self.position = position;
             let idx = self.read_var_s33()?;
-            if idx < 0 || idx > (core::u32::MAX as i64) {
+            if idx < 0 || idx > (std::u32::MAX as i64) {
                 return Err(BinaryReaderError {
                     message: "invalid function type",
                     offset: position,

src/lib.rs

@@ -23,20 +23,6 @@
 //! this is not the right library for you. You could however, build such
 //! a data-structure using this library.
 
-#![cfg_attr(not(feature = "std"), no_std)]
-
-#[cfg(not(feature = "std"))]
-#[macro_use]
-extern crate alloc as std;
-#[cfg(feature = "std")]
-#[macro_use]
-extern crate std;
-
-#[cfg(not(feature = "std"))]
-use hashbrown::HashSet;
-#[cfg(feature = "std")]
-use std::collections::HashSet;
-
 pub use crate::binary_reader::BinaryReader;
 pub use crate::binary_reader::Range;
 use crate::binary_reader::SectionHeader;

src/operators_validator.rs

@@ -13,10 +13,9 @@
  * limitations under the License.
  */
 
-use core::cmp::min;
-use core::result;
+use std::cmp::min;
+use std::result;
 use std::str;
-use std::vec::Vec;
 
 use crate::primitives::{
     FuncType, GlobalType, MemoryImmediate, MemoryType, Operator, SIMDLaneIndex, TableType, Type,

src/primitives.rs

@@ -13,12 +13,9 @@
  * limitations under the License.
  */
 
-use core::result;
-use std::boxed::Box;
-use std::fmt;
-
-#[cfg(feature = "std")]
 use std::error::Error;
+use std::fmt;
+use std::result;
 
 #[derive(Debug, Copy, Clone)]
 pub struct BinaryReaderError {
@@ -28,7 +25,6 @@ pub struct BinaryReaderError {
 
 pub type Result<T> = result::Result<T, BinaryReaderError>;
 
-#[cfg(feature = "std")]
 impl Error for BinaryReaderError {}
 
 impl fmt::Display for BinaryReaderError {

src/readers/module.rs

@@ -13,8 +13,6 @@
  * limitations under the License.
  */
 
-use core::iter::{IntoIterator, Iterator};
-
 use super::{
     BinaryReader, BinaryReaderError, CustomSectionKind, Range, Result, SectionCode, SectionHeader,
 };

src/tests.rs

@@ -13,7 +13,6 @@
  * limitations under the License.
  */
 
-#[cfg(feature = "std")]
 #[cfg(test)]
 mod simple_tests {
     use crate::operators_validator::OperatorValidatorConfig;
@@ -316,7 +315,6 @@ mod simple_tests {
     }
 }
 
-#[cfg(feature = "std")]
 #[cfg(test)]
 mod wast_tests {
     use crate::operators_validator::OperatorValidatorConfig;

src/validator.rs

@@ -13,11 +13,9 @@
  * limitations under the License.
  */
 
-use super::HashSet;
-use core::result;
+use std::collections::HashSet;
+use std::result;
 use std::str;
-use std::string::String;
-use std::vec::Vec;
 
 use crate::limits::{
     MAX_WASM_FUNCTIONS, MAX_WASM_FUNCTION_LOCALS, MAX_WASM_GLOBALS, MAX_WASM_MEMORIES,