add build.rs for GDAL crate, remove version feat.

Cargo.toml

@@ -13,9 +13,6 @@ edition = "2018"
 
 [features]
 bindgen = ["gdal-sys/bindgen"]
-gdal_2_2 = ["gdal-sys/min_gdal_version_2_2"]
-gdal_2_4 = ["gdal-sys/min_gdal_version_2_4"]
-gdal_3_0 = ["gdal-sys/min_gdal_version_3_0"]
 array = ["ndarray"]
 datetime = ["chrono"]
 
@@ -25,10 +22,13 @@ failure_derive = "0.1"
 libc = "0.2"
 geo-types = "0.4"
 gdal-sys = { path = "gdal-sys", version = "0.2"}
-#gdal-sys = "0.2"
 num-traits = "0.2"
 ndarray = {version = "0.12.1", optional = true }
 chrono = { version = "0.4", optional = true }
 
+[build-dependencies]
+gdal-sys = { path = "gdal-sys", version = "0.2"}
+semver = "0.11"
+
 [workspace]
 members = ["gdal-sys"]

build.rs

@@ -0,0 +1,45 @@
+use gdal_sys;
+use semver::Version;
+
+pub fn gdal_version_info(key: &str) -> String {
+    let c_key = std::ffi::CString::new(key.as_bytes()).unwrap();
+    let version_string = unsafe {
+        let res_ptr = gdal_sys::GDALVersionInfo(c_key.as_ptr());
+        let c_res = std::ffi::CStr::from_ptr(res_ptr);
+        c_res.to_string_lossy().into_owned()
+    };
+    version_string
+}
+
+fn main() {
+    let gdal_version_string = gdal_version_info("--version"); // This expects GDAL to repond with "GDAL Semver , RELEASE DATE"
+    println!("GDAL version string: \"{}\"", gdal_version_string);
+
+    let semver_substring = &gdal_version_string[4..gdal_version_string.find(",").unwrap_or(12)];
+    println!("GDAL semver string: \"{}\"", semver_substring);
+
+    let detected_version = Version::parse(semver_substring).expect("Could not parse gdal version!");
+
+    println!("cargo:rustc-cfg=gdal_{}", detected_version.major);
+    println!(
+        "cargo:rustc-cfg=gdal_{}_{}",
+        detected_version.major, detected_version.minor
+    );
+    println!(
+        "cargo:rustc-cfg=gdal_{}_{}_{}",
+        detected_version.major, detected_version.minor, detected_version.patch
+    );
+
+    // we only support GDAL >= 2.0.
+    for major in 2..=detected_version.major {
+        println!("cargo:rustc-cfg=major_ge_{}", major);
+    }
+
+    for minor in 0..=detected_version.minor {
+        println!("cargo:rustc-cfg=minor_ge_{}", minor);
+    }
+
+    for patch in 0..=detected_version.patch {
+        println!("cargo:rustc-cfg=patch_ge_{}", patch);
+    }
+}