Add fasta::build function + FaidxBuildError rust_htslib::errors::Erro…

…r enum entry.

src/errors.rs

@@ -33,6 +33,8 @@ pub enum Error {
     FaidxPositionTooLarge,
     #[error("bad conversion of sequence name")]
     FaidxBadSeqName,
+    #[error("failed to build index for fasta file {path:?}")]
+    FaidxBuildFailed { path: std::path::PathBuf },
 
     // Errors for Tbx
     #[error("previous iterator generation failed")]

src/faidx/mod.rs

@@ -22,6 +22,31 @@ pub struct Reader {
     inner: *mut htslib::faidx_t,
 }
 
+///
+/// Build a faidx for input path.
+///
+/// # Errors
+/// If indexing fails. Could be malformatted or file could not be accessible.
+///
+///```
+/// use rust_htslib::faidx::build;
+/// let path = std::path::PathBuf::from(concat!(env!("CARGO_MANIFEST_DIR"),"/test/test_cram.fa"));
+/// build(&path).expect("Failed to build fasta index");
+///```
+///
+pub fn build(
+    path: impl Into<std::path::PathBuf>,
+) -> Result<(), std::boxed::Box<dyn std::error::Error>> {
+    let path = path.into();
+    let os_path = std::ffi::CString::new(path.display().to_string())?;
+    let rc = unsafe { htslib::fai_build(os_path.as_ptr()) };
+    if rc < 0 {
+        Err(Error::FaidxBuildFailed { path })?
+    } else {
+        Ok(())
+    }
+}
+
 impl Reader {
     /// Create a new Reader from a path.
     ///