lib: data-stack - Rename lowwater to left_lowwater

This describes its behavior better. Also add a comment explaining what
exactly it is.

diff --git a/src/lib/data-stack.c b/src/lib/data-stack.c
index 1c8ed4e3a7ab932689e9938f7259407a4a87508d..d08ec5e87825c2d1c5aea3dcc392a1dcd4566e6b 100644 (file)
--- a/src/lib/data-stack.c
+++ b/src/lib/data-stack.c
@@ -29,7 +29,11 @@
 struct stack_block {
        struct stack_block *next;
 
-       size_t size, left, lowwater;
+       size_t size, left;
+       /* The lowest value that "left" has been in this block since it was
+          last popped. This is used to keep track which parts of the block
+          needs to be cleared if clean_after_pop is set. */
+       size_t left_lowwater;
        /* NULL or a poison value, just in case something accesses
           the memory in front of an allocated area */
        void *canary;
@@ -296,13 +300,13 @@ void t_pop_last_unsafe(void)
 
                pos = current_block->size -
                        current_frame_block->block_space_left[frame_pos];
-               used_size = current_block->size - current_block->lowwater;
+               used_size = current_block->size - current_block->left_lowwater;
                i_assert(used_size >= pos);
                memset(STACK_BLOCK_DATA(current_block) + pos, CLEAR_CHR,
                       used_size - pos);
        }
        current_block->left = current_frame_block->block_space_left[frame_pos];
-       current_block->lowwater = current_block->left;
+       current_block->left_lowwater = current_block->left;
 
        if (current_block->next != NULL) {
                /* free unused blocks */
@@ -367,7 +371,7 @@ static struct stack_block *mem_block_alloc(size_t min_size)
        }
        block->size = alloc_size;
        block->left = 0;
-       block->lowwater = block->size;
+       block->left_lowwater = block->size;
        block->next = NULL;
        block->canary = BLOCK_CANARY;
 
@@ -432,8 +436,8 @@ static void *t_malloc_real(size_t size, bool permanent)
        /* enough space in current block, use it */
        ret = data_stack_after_last_alloc(current_block);
 
-       if (current_block->left - alloc_size < current_block->lowwater)
-               current_block->lowwater = current_block->left - alloc_size;
+       if (current_block->left - alloc_size < current_block->left_lowwater)
+               current_block->left_lowwater = current_block->left - alloc_size;
        if (permanent)
                current_block->left -= alloc_size;
 
@@ -510,8 +514,8 @@ t_try_realloc(void *mem, size_t size)
                if (current_block->left >= alloc_growth) {
                        /* just shrink the available size */
                        current_block->left -= alloc_growth;
-                       if (current_block->left < current_block->lowwater)
-                               current_block->lowwater = current_block->left;
+                       if (current_block->left < current_block->left_lowwater)
+                               current_block->left_lowwater = current_block->left;
                        current_frame_block->last_alloc_size[frame_pos] =
                                new_alloc_size;
 #ifdef DEBUG