From 8195508f37bd5fa04cf474a0139c71129392c3b5 Mon Sep 17 00:00:00 2001
From: David Sterba <dsterba@suse.com>
Date: Wed, 30 Nov 2022 15:29:53 +0100
Subject: [PATCH] btrfs-progs: string-table: add ranged API for printing and
 clearing

Track how many rows belong to a header (names and separators) so they
can be printed or cleared separately. The rest is body that could be
cleared and filled repeatedly. The ranged API allows to print any number
of rows if the table is filled partially.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 common/string-table.c | 42 +++++++++++++++++++++++++++++++++++++-----
 common/string-table.h | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 68 insertions(+), 6 deletions(-)

diff --git a/common/string-table.c b/common/string-table.c
index dc9a5f74..298066ce 100644
--- a/common/string-table.c
+++ b/common/string-table.c
@@ -20,6 +20,7 @@
 #include <stdarg.h>
 #include "common/messages.h"
 #include "common/string-table.h"
+#include "common/internal.h"
 
 /*
  * Create an array of char* which will point to table cell strings
@@ -88,6 +89,8 @@ char *table_printf(struct string_table *tab, unsigned int column, unsigned int r
 
 /*
  * Print the table to stdout, interpret the alignment and expand specifiers.
+ * @from:    row from which to start
+ * @to:      upper row limit (not inclusive), 0 for the whole table
  *
  * Formatting:
  * <TEXT - the TEXT is left aligned
@@ -95,14 +98,26 @@ char *table_printf(struct string_table *tab, unsigned int column, unsigned int r
  * =     - the cell text will be filled by ===== (column width)
  * *C    - the cell text will be filled by character C (column width)
  */
-void table_dump(struct string_table *tab)
+void table_dump_range(struct string_table *tab, unsigned int from, unsigned int to)
 {
-	int sizes[tab->ncols];
-	int i, j;
+	unsigned int sizes[tab->ncols];
+	unsigned int i, j;
+	unsigned int prescan;
+
+	if (to == 0)
+		to = tab->nrows;
+
+	if (from > to) {
+		error("invalid range for table dump %u > %u", from, to);
+		return;
+	}
+
+	prescan = max_t(unsigned int, 100, to);
+	prescan = min_t(unsigned int, tab->nrows, prescan);
 
 	for (i = 0; i < tab->ncols; i++) {
 		sizes[i] = 0;
-		for (j = 0; j < tab->nrows; j++) {
+		for (j = 0; j < prescan; j++) {
 			int idx = i + j * tab->ncols;
 			int len;
 
@@ -118,7 +133,7 @@ void table_dump(struct string_table *tab)
 		}
 	}
 
-	for (j = 0; j < tab->nrows; j++) {
+	for (j = from; j < to; j++) {
 		for (i = 0; i < tab->ncols; i++) {
 			int idx = i + j * tab->ncols;
 			char *cell = tab->cells[idx];
@@ -160,3 +175,20 @@ void table_free(struct string_table *tab)
 
 	free(tab);
 }
+
+void table_clear_range(struct string_table *tab, unsigned int from, unsigned int to)
+{
+	unsigned int row, col;
+
+	if (to == 0)
+		to = tab->nrows;
+
+	for (row = from; row < to; row++) {
+		char **rowstart = &tab->cells[row * tab->ncols];
+
+		for (col = 0; col < tab->ncols; col++) {
+			free(rowstart[col]);
+			rowstart[col] = NULL;
+		}
+	}
+}
diff --git a/common/string-table.h b/common/string-table.h
index ab5f7d66..cdc066fa 100644
--- a/common/string-table.h
+++ b/common/string-table.h
@@ -27,6 +27,8 @@ enum string_table_spacing {
 struct string_table {
 	unsigned int ncols;
 	unsigned int nrows;
+	/* How many rows are header (names and separators). */
+	unsigned int hrows;
 	enum string_table_spacing spacing;
 	char *cells[];
 };
@@ -37,7 +39,35 @@ char *table_printf(struct string_table *tab, unsigned int column, unsigned int r
 			  const char *fmt, ...);
 char *table_vprintf(struct string_table *tab, unsigned int column, unsigned int row,
 			  const char *fmt, va_list ap);
-void table_dump(struct string_table *tab);
 void table_free(struct string_table *tab);
 
+void table_dump_range(struct string_table *tab, unsigned int from, unsigned int to);
+
+static inline void table_dump(struct string_table *tab)
+{
+	table_dump_range(tab, 0, 0);
+}
+
+static inline void table_dump_header(struct string_table *tab)
+{
+	table_dump_range(tab, 0, tab->hrows);
+}
+
+static inline void table_dump_body(struct string_table *tab)
+{
+	table_dump_range(tab, tab->hrows, 0);
+}
+
+void table_clear_range(struct string_table *tab, unsigned int from, unsigned int to);
+
+static inline void table_clear_header(struct string_table *tab)
+{
+	table_clear_range(tab, 0, tab->hrows);
+}
+
+static inline void table_clear_body(struct string_table *tab)
+{
+	table_clear_range(tab, tab->hrows, 0);
+}
+
 #endif