Merge #364

364: Add CslStringList::add_string r=lnicola a=jshrake

- [x] I agree to follow the project's [code of conduct](https://github.com/georust/gdal/blob/master/CODE_OF_CONDUCT.md).
- [x] I added an entry to `CHANGES.md` if knowledge of this change could be valuable to users.
---

This method wraps gdal_sys::CSLAddString.

This method is useful when constructing argument lists for option structs for the various utility functions found in gdal_utils, such as GDALWarp and GDALTranslate.


Co-authored-by: Justin Shrake <justinshrake@gmail.com>

CHANGES.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- Added `CslStringList::add_string`
+
+  - <https://github.com/georust/gdal/pull/364>
+
 - **Possibly breaking**: Set MSRV to 1.58.
 
   - <https://github.com/georust/gdal/pull/363>

src/cpl.rs

@@ -7,7 +7,9 @@ use std::ffi::CString;
 use std::fmt::{Debug, Formatter};
 use std::ptr;
 
-use gdal_sys::{CSLCount, CSLDestroy, CSLDuplicate, CSLFetchNameValue, CSLSetNameValue};
+use gdal_sys::{
+    CSLAddString, CSLCount, CSLDestroy, CSLDuplicate, CSLFetchNameValue, CSLSetNameValue,
+};
 use libc::c_char;
 
 use crate::errors::{GdalError, Result};
@@ -57,6 +59,17 @@ impl CslStringList {
         Ok(())
     }
 
+    /// Adds the string `value` to the list.
+    ///
+    /// Returns `Ok<()>` on success, `Err<GdalError>` if `value` cannot be converted to a C string.
+    ///
+    /// See: [`CSLAddString`](https://gdal.org/api/cpl.html#_CPPv412CSLAddStringPPcPKc)
+    pub fn add_string(&mut self, value: &str) -> Result<()> {
+        let v = CString::new(value)?;
+        self.list_ptr = unsafe { CSLAddString(self.list_ptr, v.as_ptr()) };
+        Ok(())
+    }
+
     /// Looks up the value corresponding to `key`.
     ///
     /// See [`CSLFetchNameValue`](https://gdal.org/doxygen/cpl__string_8h.html#a4f23675f8b6f015ed23d9928048361a1)
@@ -269,4 +282,17 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn can_add_strings() -> Result<()> {
+        let mut l = CslStringList::new();
+        assert!(l.is_empty());
+        l.add_string("-abc")?;
+        l.add_string("-d_ef")?;
+        l.add_string("A")?;
+        l.add_string("B")?;
+        assert_eq!(l.len(), 4);
+
+        Ok(())
+    }
 }