Add java support (using JNA)

This builds on #853 and adds a new language backend capable of
generating java bindings.

The generated bindings use [JNA](https://github.com/java-native-access/jna)
(I used the last version 5.13.0 while developping but this will probably
work with earlier ones as well)

Most of the new code lives in `bindgen/language_backend/java_jna.rs` and
is pretty straightfowards generation as most on the complicated things were done
in the previous refactoring.

The test suite has been updated to generate and compile the bindings for
java when running. On nice thing gained with this is the possibilibty to
put a configuration file specific to a language alongside the stardard
one and the test will take this one instead of the default one if it
exists (quite a few test use the `header` config to add some more code
inside the generated bindings, C or preprocessor code doesn't work well
in a java source file :P)

All tests are green, but that doesn't mean all the generated bindings
are correct, some cases may fail at runtime as I didn't test all
cases in a real program. I did however generate and use the bindings on a
non trivial lib I'm developping and they worked as expected.

src/bindgen/bindings.rs

@@ -16,7 +16,8 @@ use crate::bindgen::ir::{
     Constant, Function, ItemContainer, ItemMap, Path as BindgenPath, Static, Struct, Type, Typedef,
 };
 use crate::bindgen::language_backend::{
-    CLikeLanguageBackend, CythonLanguageBackend, LanguageBackend, NamespaceOperation,
+    CLikeLanguageBackend, CythonLanguageBackend, JavaJnaLanguageBackend, LanguageBackend,
+    NamespaceOperation,
 };
 use crate::bindgen::writer::SourceWriter;
 
@@ -36,6 +37,7 @@ pub struct Bindings {
     /// Bindings are generated by a recursive call to cbindgen
     /// and shouldn't do anything when written anywhere.
     noop: bool,
+    binding_crate_lib_name: String,
 }
 
 impl Bindings {
@@ -50,6 +52,7 @@ impl Bindings {
         functions: Vec<Function>,
         source_files: Vec<path::PathBuf>,
         noop: bool,
+        binding_crate_lib_name: String,
     ) -> Bindings {
         Bindings {
             config,
@@ -62,6 +65,7 @@ impl Bindings {
             functions,
             source_files,
             noop,
+            binding_crate_lib_name,
         }
     }
 
@@ -207,6 +211,10 @@ impl Bindings {
             Language::Cython => {
                 self.write_with_backend(file, &CythonLanguageBackend::new(&self.config))
             }
+            Language::JavaJna => self.write_with_backend(
+                file,
+                &JavaJnaLanguageBackend::new(&self.config, self.binding_crate_lib_name.clone()),
+            ),
         }
     }
 

src/bindgen/builder.rs

@@ -361,6 +361,7 @@ impl Builder {
                 Default::default(),
                 Default::default(),
                 true,
+                Default::default(),
             ));
         }
 
@@ -405,6 +406,9 @@ impl Builder {
             result.typedefs,
             result.functions,
             result.source_files,
+            self.lib_cargo
+                .map(|cargo| cargo.binding_crate_lib_name().to_string())
+                .unwrap_or_default(),
         )
         .generate()
     }

src/bindgen/cargo/cargo.rs

@@ -25,6 +25,7 @@ fn parse_dep_string(dep_string: &str) -> (&str, Option<&str>) {
 pub(crate) struct Cargo {
     manifest_path: PathBuf,
     binding_crate_name: String,
+    binding_crate_lib_name: String,
     lock: Option<Lock>,
     metadata: Metadata,
     clean: bool,
@@ -63,19 +64,24 @@ impl Cargo {
             None
         };
 
+        let manifest = cargo_toml::manifest(&toml_path)
+            .map_err(|x| Error::CargoToml(toml_path.to_str().unwrap().to_owned(), x))?;
+
         // Use the specified binding crate name or infer it from the manifest
         let binding_crate_name = match binding_crate_name {
             Some(s) => s.to_owned(),
-            None => {
-                let manifest = cargo_toml::manifest(&toml_path)
-                    .map_err(|x| Error::CargoToml(toml_path.to_str().unwrap().to_owned(), x))?;
-                manifest.package.name
-            }
+            None => manifest.package.name,
         };
 
+        let binding_crate_lib_name = manifest
+            .lib
+            .and_then(|lib| lib.name)
+            .unwrap_or_else(|| binding_crate_name.clone());
+
         Ok(Cargo {
             manifest_path: toml_path,
             binding_crate_name,
+            binding_crate_lib_name,
             lock,
             metadata,
             clean,
@@ -86,6 +92,10 @@ impl Cargo {
         &self.binding_crate_name
     }
 
+    pub(crate) fn binding_crate_lib_name(&self) -> &str {
+        &self.binding_crate_lib_name
+    }
+
     pub(crate) fn binding_crate_ref(&self) -> PackageRef {
         match self.find_pkg_ref(&self.binding_crate_name) {
             Some(pkg_ref) => pkg_ref,

src/bindgen/cargo/cargo_toml.rs

@@ -50,13 +50,19 @@ impl error::Error for Error {
 #[derive(Clone, Deserialize, Debug)]
 pub struct Manifest {
     pub package: Package,
+    pub lib: Option<Lib>,
 }
 
 #[derive(Clone, Deserialize, Debug)]
 pub struct Package {
     pub name: String,
 }
 
+#[derive(Clone, Deserialize, Debug)]
+pub struct Lib {
+    pub name: Option<String>,
+}
+
 /// Parse the Cargo.toml for a given path
 pub fn manifest(manifest_path: &Path) -> Result<Manifest, Error> {
     let mut s = String::new();

src/bindgen/config.rs

@@ -4,6 +4,7 @@
 
 use std::collections::{BTreeMap, HashMap};
 use std::default::Default;
+use std::fmt::{Display, Formatter};
 use std::str::FromStr;
 use std::{fmt, fs, path::Path as StdPath, path::PathBuf as StdPathBuf};
 
@@ -23,6 +24,7 @@ pub enum Language {
     Cxx,
     C,
     Cython,
+    JavaJna,
 }
 
 impl FromStr for Language {
@@ -42,18 +44,48 @@ impl FromStr for Language {
             "C" => Ok(Language::C),
             "cython" => Ok(Language::Cython),
             "Cython" => Ok(Language::Cython),
+            "Java-JNA" => Ok(Language::JavaJna),
+            "Java-Jna" => Ok(Language::JavaJna),
+            "java-jna" => Ok(Language::JavaJna),
+            "JavaJNA" => Ok(Language::JavaJna),
+            "JavaJna" => Ok(Language::JavaJna),
+            "javajna" => Ok(Language::JavaJna),
             _ => Err(format!("Unrecognized Language: '{}'.", s)),
         }
     }
 }
 
+impl Display for Language {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "{}",
+            match self {
+                Language::Cxx => {
+                    "cxx"
+                }
+                Language::C => {
+                    "c"
+                }
+                Language::Cython => {
+                    "cython"
+                }
+                Language::JavaJna => {
+                    "java-jna"
+                }
+            }
+        )
+    }
+}
+
 deserialize_enum_str!(Language);
 
 impl Language {
     pub(crate) fn typedef(self) -> &'static str {
         match self {
             Language::Cxx | Language::C => "typedef",
             Language::Cython => "ctypedef",
+            _ => unimplemented!(),
         }
     }
 }
@@ -897,6 +929,22 @@ pub struct CythonConfig {
     pub cimports: BTreeMap<String, Vec<String>>,
 }
 
+/// Settings specific to Java bindings.
+#[derive(Debug, Clone, Default, Deserialize)]
+#[serde(rename_all = "snake_case")]
+#[serde(deny_unknown_fields)]
+#[serde(default)]
+pub struct JavaConfig {
+    /// Package to use
+    pub package: Option<String>,
+
+    /// Name of the generated interface
+    pub interface_name: Option<String>,
+
+    /// Extra definition to include inside the generated interface
+    pub extra_defs: Option<String>,
+}
+
 /// A collection of settings to customize the generated bindings.
 #[derive(Debug, Clone, Deserialize)]
 #[serde(rename_all = "snake_case")]
@@ -1019,6 +1067,8 @@ pub struct Config {
     pub only_target_dependencies: bool,
     /// Configuration options specific to Cython.
     pub cython: CythonConfig,
+    /// Configuration options specific to Java (JNA backend)
+    pub java_jna: JavaConfig,
     #[serde(skip)]
     pub(crate) config_path: Option<StdPathBuf>,
 }
@@ -1063,6 +1113,7 @@ impl Default for Config {
             pointer: PtrConfig::default(),
             only_target_dependencies: false,
             cython: CythonConfig::default(),
+            java_jna: JavaConfig::default(),
             config_path: None,
         }
     }

src/bindgen/ir/cfg.rs

@@ -336,29 +336,43 @@ pub trait ConditionWrite {
 impl ConditionWrite for Option<Condition> {
     fn write_before<F: Write>(&self, config: &Config, out: &mut SourceWriter<F>) {
         if let Some(ref cfg) = *self {
-            if config.language == Language::Cython {
-                out.write("IF ");
-                cfg.write(config, out);
-                out.open_brace();
-            } else {
-                out.push_set_spaces(0);
-                out.write("#if ");
-                cfg.write(config, out);
-                out.pop_set_spaces();
-                out.new_line();
+            match config.language {
+                Language::Cython => {
+                    out.write("IF ");
+                    cfg.write(config, out);
+                    out.open_brace();
+                }
+                Language::Cxx | Language::C => {
+                    out.push_set_spaces(0);
+                    out.write("#if ");
+                    cfg.write(config, out);
+                    out.pop_set_spaces();
+                    out.new_line();
+                }
+                Language::JavaJna => {
+                    write!(out, "/* begin condition not supported  {self:?} */");
+                    out.new_line();
+                }
             }
         }
     }
 
     fn write_after<F: Write>(&self, config: &Config, out: &mut SourceWriter<F>) {
         if self.is_some() {
-            if config.language == Language::Cython {
-                out.close_brace(false);
-            } else {
-                out.new_line();
-                out.push_set_spaces(0);
-                out.write("#endif");
-                out.pop_set_spaces();
+            match config.language {
+                Language::Cython => {
+                    out.close_brace(false);
+                }
+                Language::Cxx | Language::C => {
+                    out.new_line();
+                    out.push_set_spaces(0);
+                    out.write("#endif");
+                    out.pop_set_spaces();
+                }
+                Language::JavaJna => {
+                    out.new_line();
+                    write!(out, "/* end condition not supported  {self:?} */");
+                }
             }
         }
     }

src/bindgen/ir/constant.rs

@@ -16,7 +16,7 @@ use crate::bindgen::ir::{
     AnnotationSet, Cfg, ConditionWrite, Documentation, GenericParams, Item, ItemContainer, Path,
     Struct, ToCondition, Type,
 };
-use crate::bindgen::language_backend::LanguageBackend;
+use crate::bindgen::language_backend::{java_writable_literal, wrap_java_value, LanguageBackend};
 use crate::bindgen::library::Library;
 use crate::bindgen::writer::SourceWriter;
 use crate::bindgen::Bindings;
@@ -708,6 +708,22 @@ impl Constant {
                 write!(out, " {} # = ", name);
                 language_backend.write_literal(out, value);
             }
+            Language::JavaJna => {
+                if java_writable_literal(&self.ty, value) {
+                    out.write("public static final ");
+                    language_backend.write_type(out, &self.ty);
+                    write!(out, " {}  = ", self.export_name);
+                    language_backend.write_literal(out, &wrap_java_value(value, &self.ty));
+                    out.write(";")
+                } else {
+                    write!(
+                        out,
+                        "/* Unsupported literal for constant {} */",
+                        self.export_name
+                    )
+                }
+                out.new_line();
+            }
         }
 
         condition.write_after(config, out);

src/bindgen/ir/enumeration.rs

@@ -721,6 +721,7 @@ impl Enum {
                     write!(out, "{}enum {}", config.style.cython_def(), tag_name);
                 }
             }
+            _ => unimplemented!(),
         }
         out.open_brace();
 
@@ -775,6 +776,7 @@ impl Enum {
             Language::C if config.style.generate_typedef() => out.write("typedef "),
             Language::C | Language::Cxx => {}
             Language::Cython => out.write(config.style.cython_def()),
+            _ => unimplemented!(),
         }
 
         out.write(if inline_tag_field { "union" } else { "struct" });

src/bindgen/language_backend/clike.rs

@@ -975,14 +975,15 @@ impl LanguageBackend for CLikeLanguageBackend<'_> {
                         return write!(out, "{}", known);
                     }
                     let path_separator = match self.config.language {
-                        Language::Cython | Language::C => "_",
+                        Language::C => "_",
                         Language::Cxx => {
                             if self.config.structure.associated_constants_in_body {
                                 "::"
                             } else {
                                 "_"
                             }
                         }
+                        _ => unreachable!(),
                     };
                     write!(out, "{}{}", export_name, path_separator)
                 }