[Tarantool-patches] [PATCH v4 14/53] sql: rework mem_move()

[Mergen Imeev via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

This patch reworks mem_move(). This function moves all content of source
MEM to destination MEM. Source mem is set to NULL.

Part of #5818
---
 src/box/sql/mem.c     | 57 +++++++++----------------------------------
 src/box/sql/mem.h     |  8 ++++--
 src/box/sql/vdbe.c    | 29 ++--------------------
 src/box/sql/vdbeapi.c |  2 +-
 4 files changed, 20 insertions(+), 76 deletions(-)

diff --git a/src/box/sql/mem.c b/src/box/sql/mem.c
index 30c568970..3d42ac63c 100644
--- a/src/box/sql/mem.c
+++ b/src/box/sql/mem.c
@@ -308,6 +308,17 @@ mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from)
 	return 0;
 }
 
+int
+mem_move(struct Mem *to, struct Mem *from)
+{
+	mem_destroy(to);
+	memcpy(to, from, sizeof(*to));
+	from->flags = MEM_Null;
+	from->szMalloc = 0;
+	from->zMalloc = NULL;
+	return 0;
+}
+
 static inline bool
 mem_has_msgpack_subtype(struct Mem *mem)
 {
@@ -2033,52 +2044,6 @@ vdbe_mem_alloc_blob_region(struct Mem *vdbe_mem, uint32_t size)
 	return 0;
 }
 
-/*
- * Transfer the contents of pFrom to pTo. Any existing value in pTo is
- * freed. If pFrom contains ephemeral data, a copy is made.
- *
- * pFrom contains an SQL NULL when this routine returns.
- */
-void
-sqlVdbeMemMove(Mem * pTo, Mem * pFrom)
-{
-	assert(pFrom->db == 0 || pTo->db == 0 || pFrom->db == pTo->db);
-
-	mem_destroy(pTo);
-	memcpy(pTo, pFrom, sizeof(Mem));
-	pFrom->flags = MEM_Null;
-	pFrom->szMalloc = 0;
-}
-
-/*
- * Change pMem so that its MEM_Str or MEM_Blob value is stored in
- * MEM.zMalloc, where it can be safely written.
- *
- * Return 0 on success or -1 if malloc fails.
- */
-int
-sqlVdbeMemMakeWriteable(Mem * pMem)
-{
-	if ((pMem->flags & (MEM_Str | MEM_Blob)) != 0) {
-		if (ExpandBlob(pMem))
-			return -1;
-		if (pMem->szMalloc == 0 || pMem->z != pMem->zMalloc) {
-			if (sqlVdbeMemGrow(pMem, pMem->n + 2, 1)) {
-				return -1;
-			}
-			pMem->z[pMem->n] = 0;
-			pMem->z[pMem->n + 1] = 0;
-			pMem->flags |= MEM_Term;
-		}
-	}
-	pMem->flags &= ~MEM_Ephem;
-#ifdef SQL_DEBUG
-	pMem->pScopyFrom = 0;
-#endif
-
-	return 0;
-}
-
 int
 sql_vdbemem_finalize(struct Mem *mem, struct func *func)
 {
diff --git a/src/box/sql/mem.h b/src/box/sql/mem.h
index 58220d215..801f3cba6 100644
--- a/src/box/sql/mem.h
+++ b/src/box/sql/mem.h
@@ -179,6 +179,12 @@ mem_copy(struct Mem *to, const struct Mem *from);
 int
 mem_copy_as_ephemeral(struct Mem *to, const struct Mem *from);
 
+/**
+ * Move all content of source MEM to destination MEM. Source MEM is set to NULL.
+ */
+int
+mem_move(struct Mem *to, struct Mem *from);
+
 /* One or more of the following flags are set to indicate the validOK
  * representations of the value stored in the Mem struct.
  *
@@ -495,8 +501,6 @@ mem_is_type_compatible(struct Mem *mem, enum field_type type);
 
 int
 vdbe_mem_alloc_blob_region(struct Mem *vdbe_mem, uint32_t size);
-void sqlVdbeMemMove(Mem *, Mem *);
-int sqlVdbeMemMakeWriteable(Mem *);
 
 /**
  * Memory cell mem contains the context of an aggregate function.
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index 55083fb23..4654b1610 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -165,21 +165,6 @@ vdbeTakeBranch(int iSrcLine, u8 I, u8 M)
 }
 #endif
 
-/*
- * An ephemeral string value (signified by the MEM_Ephem flag) contains
- * a pointer to a dynamically allocated string where some other entity
- * is responsible for deallocating that string.  Because the register
- * does not control the string, it might be deleted without the register
- * knowing it.
- *
- * This routine converts an ephemeral string into a dynamically allocated
- * string that the register itself controls.  In other words, it
- * converts an MEM_Ephem string into a string with P.z==P.zMalloc.
- */
-#define Deephemeralize(P)					\
-	if (((P)->flags&MEM_Ephem)!=0				\
-	    && sqlVdbeMemMakeWriteable(P)) { goto no_mem;}
-
 /* Return true if the cursor was opened using the OP_OpenSorter opcode. */
 #define isSorter(x) ((x)->eCurType==CURTYPE_SORTER)
 
@@ -949,13 +934,7 @@ case OP_Move: {
 		assert(pIn1<=&aMem[(p->nMem+1 - p->nCursor)]);
 		assert(memIsValid(pIn1));
 		memAboutToChange(p, pOut);
-		sqlVdbeMemMove(pOut, pIn1);
-#ifdef SQL_DEBUG
-		if (pOut->pScopyFrom>=&aMem[p1] && pOut->pScopyFrom<pOut) {
-			pOut->pScopyFrom += pOp->p2 - p1;
-		}
-#endif
-		Deephemeralize(pOut);
+		mem_move(pOut, pIn1);
 		REGISTER_TRACE(p, p2++, pOut);
 		pIn1++;
 		pOut++;
@@ -979,11 +958,7 @@ case OP_Copy: {
 	pOut = &aMem[pOp->p2];
 	assert(pOut!=pIn1);
 	while( 1) {
-		mem_copy_as_ephemeral(pOut, pIn1);
-		Deephemeralize(pOut);
-#ifdef SQL_DEBUG
-		pOut->pScopyFrom = 0;
-#endif
+		mem_copy(pOut, pIn1);
 		REGISTER_TRACE(p, pOp->p2+pOp->p3-n, pOut);
 		if ((n--)==0) break;
 		pOut++;
diff --git a/src/box/sql/vdbeapi.c b/src/box/sql/vdbeapi.c
index b13385647..2625a9115 100644
--- a/src/box/sql/vdbeapi.c
+++ b/src/box/sql/vdbeapi.c
@@ -980,7 +980,7 @@ sqlTransferBindings(sql_stmt * pFromStmt, sql_stmt * pToStmt)
 	assert(pTo->db == pFrom->db);
 	assert(pTo->nVar == pFrom->nVar);
 	for (i = 0; i < pFrom->nVar; i++) {
-		sqlVdbeMemMove(&pTo->aVar[i], &pFrom->aVar[i]);
+		mem_move(&pTo->aVar[i], &pFrom->aVar[i]);
 	}
 	return 0;
 }
-- 
2.25.1