feat(cli): move summary display predicates to Rust

Port the single-file and multiple-file summary decisions through the existing FIO context ABI, including the display-level lookup and the original multiple-file assertion invariant. Keep the C wrappers and call sites unchanged.

Test Plan: cargo test --manifest-path rust/cli/Cargo.toml --no-default-features --features cli,compression,decompression,benchmark (108 passed); CLI all-target clippy; make -B -C programs -j2 zstd zstd-small zstd-frugal; make -C tests -j2 test-cli-tests (41 passed).

programs/fileio.c

@@ -283,16 +283,17 @@ typedef char FIO_rust_ctx_size[
         (sizeof(FIO_ctx_t)
          == offsetof(FIO_ctx_t, totalBytesOutput) + sizeof(size_t)) ? 1 : -1];
 
+int FIO_rust_shouldDisplayFileSummary(const FIO_ctx_t* fCtx);
+int FIO_rust_shouldDisplayMultipleFileSummary(const FIO_ctx_t* fCtx);
+
 static int FIO_shouldDisplayFileSummary(FIO_ctx_t const* fCtx)
 {
-    return fCtx->nbFilesTotal <= 1 || g_display_prefs.displayLevel >= 3;
+    return FIO_rust_shouldDisplayFileSummary(fCtx);
 }
 
 static int FIO_shouldDisplayMultipleFileSummary(FIO_ctx_t const* fCtx)
 {
-    int const shouldDisplay = (fCtx->nbFilesProcessed >= 1 && fCtx->nbFilesTotal > 1);
-    assert(shouldDisplay || FIO_shouldDisplayFileSummary(fCtx) || fCtx->nbFilesProcessed == 0);
-    return shouldDisplay;
+    return FIO_rust_shouldDisplayMultipleFileSummary(fCtx);
 }
 
 

rust/src/fileio_prefs.rs

@@ -497,6 +497,29 @@ pub unsafe extern "C" fn FIO_setHasStdinInput(ctx: *mut FIO_ctx_t, value: c_int)
     unsafe { ptr::addr_of_mut!((*ctx).hasStdinInput).write(c_int::from(value != 0)) };
 }
 
+#[inline]
+fn should_display_file_summary(ctx: &FIO_ctx_t) -> bool {
+    ctx.nbFilesTotal <= 1 || unsafe { (*display_prefs()).displayLevel >= 3 }
+}
+
+/// Return whether the single-file summary should be displayed.
+#[no_mangle]
+pub unsafe extern "C" fn FIO_rust_shouldDisplayFileSummary(ctx: *const FIO_ctx_t) -> c_int {
+    let ctx = unsafe { &*ctx };
+    c_int::from(should_display_file_summary(ctx))
+}
+
+/// Return whether the multiple-file summary should be displayed.
+///
+/// The assertion mirrors the original C helper's invariant exactly.
+#[no_mangle]
+pub unsafe extern "C" fn FIO_rust_shouldDisplayMultipleFileSummary(ctx: *const FIO_ctx_t) -> c_int {
+    let ctx = unsafe { &*ctx };
+    let should_display = ctx.nbFilesProcessed >= 1 && ctx.nbFilesTotal > 1;
+    assert!(should_display || should_display_file_summary(ctx) || ctx.nbFilesProcessed == 0);
+    c_int::from(should_display)
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn FIO_determineHasStdinInput(
     ctx: *mut FIO_ctx_t,
@@ -1349,6 +1372,76 @@ mod tests {
         unsafe { FIO_freeContext(ctx) };
     }
 
+    fn summary_context(nb_files_total: c_int, nb_files_processed: c_int) -> FIO_ctx_t {
+        FIO_ctx_t {
+            nbFilesTotal: nb_files_total,
+            hasStdinInput: 0,
+            hasStdoutOutput: 0,
+            currFileIdx: 0,
+            nbFilesProcessed: nb_files_processed,
+            totalBytesInput: 0,
+            totalBytesOutput: 0,
+        }
+    }
+
+    #[test]
+    fn file_summary_display_matches_file_count_and_display_level() {
+        let mut ctx = summary_context(1, 0);
+
+        for display_level in [0, 2] {
+            FIO_setNotificationLevel(display_level);
+            assert_eq!(unsafe { FIO_rust_shouldDisplayFileSummary(&ctx) }, 1);
+        }
+
+        ctx.nbFilesTotal = 2;
+        for display_level in [0, 2] {
+            FIO_setNotificationLevel(display_level);
+            assert_eq!(unsafe { FIO_rust_shouldDisplayFileSummary(&ctx) }, 0);
+        }
+
+        FIO_setNotificationLevel(3);
+        assert_eq!(unsafe { FIO_rust_shouldDisplayFileSummary(&ctx) }, 1);
+
+        FIO_setNotificationLevel(2);
+    }
+
+    #[test]
+    fn multiple_file_summary_display_matches_processed_count_and_file_count() {
+        let mut ctx = summary_context(2, 0);
+
+        for display_level in [0, 2, 3] {
+            FIO_setNotificationLevel(display_level);
+            assert_eq!(
+                unsafe { FIO_rust_shouldDisplayMultipleFileSummary(&ctx) },
+                0
+            );
+        }
+
+        ctx.nbFilesProcessed = 1;
+        for display_level in [0, 2, 3] {
+            FIO_setNotificationLevel(display_level);
+            assert_eq!(
+                unsafe { FIO_rust_shouldDisplayMultipleFileSummary(&ctx) },
+                1
+            );
+        }
+
+        ctx.nbFilesProcessed = 2;
+        FIO_setNotificationLevel(0);
+        assert_eq!(
+            unsafe { FIO_rust_shouldDisplayMultipleFileSummary(&ctx) },
+            1
+        );
+
+        ctx.nbFilesTotal = 1;
+        assert_eq!(
+            unsafe { FIO_rust_shouldDisplayMultipleFileSummary(&ctx) },
+            0
+        );
+
+        FIO_setNotificationLevel(2);
+    }
+
     #[test]
     fn preference_setters_update_the_c_layout() {
         let prefs = unsafe { FIO_createPreferences() };