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Improved comments on VDBE opcodes, for better documentation. No code

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or logic changes.

FossilOrigin-Name: 2d32e4876e0b162730f81e5c2658be12d64a9a99
This commit is contained in:
drh
2014-07-25 18:37:42 +00:00
parent 8af3f772c1
commit 5dad9a3497
3 changed files with 53 additions and 37 deletions
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76
src/vdbe.c
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@@ -767,12 +767,14 @@ case OP_Return: { /* in1 */
/* Opcode: InitCoroutine P1 P2 P3 * *
**
** Set up register P1 so that it will OP_Yield to the co-routine
** Set up register P1 so that it will Yield to the coroutine
** located at address P3.
**
** If P2!=0 then the co-routine implementation immediately follows
** this opcode. So jump over the co-routine implementation to
** If P2!=0 then the coroutine implementation immediately follows
** this opcode. So jump over the coroutine implementation to
** address P2.
**
** See also: EndCoroutine
*/
case OP_InitCoroutine: { /* jump */
assert( pOp->p1>0 && pOp->p1<=(p->nMem-p->nCursor) );
@@ -788,9 +790,11 @@ case OP_InitCoroutine: { /* jump */
/* Opcode: EndCoroutine P1 * * * *
**
** The instruction at the address in register P1 is an OP_Yield.
** Jump to the P2 parameter of that OP_Yield.
** The instruction at the address in register P1 is an Yield.
** Jump to the P2 parameter of that Yield.
** After the jump, register P1 becomes undefined.
**
** See also: InitCoroutine
*/
case OP_EndCoroutine: { /* in1 */
VdbeOp *pCaller;
@@ -807,11 +811,16 @@ case OP_EndCoroutine: { /* in1 */
/* Opcode: Yield P1 P2 * * *
**
** Swap the program counter with the value in register P1.
** Swap the program counter with the value in register P1. This
** has the effect of yielding to a coroutine.
**
** If the co-routine ends with OP_Yield or OP_Return then continue
** to the next instruction. But if the co-routine ends with
** OP_EndCoroutine, jump immediately to P2.
** If the coroutine that is launched by this instruction ends with
** Yield or Return then continue to the next instruction. But if
** the coroutine launched by this instruction ends with
** EndCoroutine, then jump to P2 rather than continuing with the
** next instruction.
**
** See also: InitCoroutine
*/
case OP_Yield: { /* in1, jump */
int pcDest;
@@ -2196,10 +2205,14 @@ case OP_BitNot: { /* same as TK_BITNOT, in1, out2 */
/* Opcode: Once P1 P2 * * *
**
** Check if OP_Once flag P1 is set. If so, jump to instruction P2. Otherwise,
** set the flag and fall through to the next instruction. In other words,
** this opcode causes all following opcodes up through P2 (but not including
** P2) to run just once and to be skipped on subsequent times through the loop.
** Check the "once" flag number P1. If it is set, jump to instruction P2.
** Otherwise, set the flag and fall through to the next instruction.
** In other words, this opcode causes all following opcodes up through P2
** (but not including P2) to run just once and to be skipped on subsequent
** times through the loop.
**
** All "once" flags are initially cleared whenever a prepared statement
** first begins to run.
*/
case OP_Once: { /* jump */
assert( pOp->p1<p->nOnceFlag );
@@ -3495,7 +3508,7 @@ case OP_Close: {
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end. In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
** configured to use Next, not Prev.
**
** See also: Found, NotFound, SeekLt, SeekGt, SeekLe
*/
@@ -3513,7 +3526,7 @@ case OP_Close: {
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end. In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
** configured to use Next, not Prev.
**
** See also: Found, NotFound, SeekLt, SeekGe, SeekLe
*/
@@ -3531,7 +3544,7 @@ case OP_Close: {
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning. In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
** configured to use Prev, not Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLe
*/
@@ -3549,7 +3562,7 @@ case OP_Close: {
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning. In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
** configured to use Prev, not Next.
**
** See also: Found, NotFound, SeekGt, SeekGe, SeekLt
*/
@@ -4470,7 +4483,7 @@ case OP_NullRow: {
**
** This opcode leaves the cursor configured to move in reverse order,
** from the end toward the beginning. In other words, the cursor is
** configured to use OP_Prev, not OP_Next.
** configured to use Prev, not Next.
*/
case OP_Last: { /* jump */
VdbeCursor *pC;
@@ -4530,7 +4543,7 @@ case OP_Sort: { /* jump */
**
** This opcode leaves the cursor configured to move in forward order,
** from the begining toward the end. In other words, the cursor is
** configured to use OP_Next, not OP_Prev.
** configured to use Next, not Prev.
*/
case OP_Rewind: { /* jump */
VdbeCursor *pC;
@@ -4571,9 +4584,9 @@ case OP_Rewind: { /* jump */
** to the following instruction. But if the cursor advance was successful,
** jump immediately to P2.
**
** The OP_Next opcode is only valid following an OP_SeekGT, OP_SeekGE, or
** OP_Rewind opcode used to position the cursor. OP_Next is not allowed
** to follow OP_SeekLT, OP_SeekLE, or OP_Last.
** The Next opcode is only valid following an SeekGT, SeekGE, or
** OP_Rewind opcode used to position the cursor. Next is not allowed
** to follow SeekLT, SeekLE, or OP_Last.
**
** The P1 cursor must be for a real table, not a pseudo-table. P1 must have
** been opened prior to this opcode or the program will segfault.
@@ -4593,7 +4606,7 @@ case OP_Rewind: { /* jump */
*/
/* Opcode: NextIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like OP_Next except that if cursor P1 is not
** This opcode works just like Next except that if cursor P1 is not
** open it behaves a no-op.
*/
/* Opcode: Prev P1 P2 P3 P4 P5
@@ -4604,9 +4617,9 @@ case OP_Rewind: { /* jump */
** jump immediately to P2.
**
**
** The OP_Prev opcode is only valid following an OP_SeekLT, OP_SeekLE, or
** OP_Last opcode used to position the cursor. OP_Prev is not allowed
** to follow OP_SeekGT, OP_SeekGE, or OP_Rewind.
** The Prev opcode is only valid following an SeekLT, SeekLE, or
** OP_Last opcode used to position the cursor. Prev is not allowed
** to follow SeekGT, SeekGE, or OP_Rewind.
**
** The P1 cursor must be for a real table, not a pseudo-table. If P1 is
** not open then the behavior is undefined.
@@ -4624,7 +4637,7 @@ case OP_Rewind: { /* jump */
*/
/* Opcode: PrevIfOpen P1 P2 P3 P4 P5
**
** This opcode works just like OP_Prev except that if cursor P1 is not
** This opcode works just like Prev except that if cursor P1 is not
** open it behaves a no-op.
*/
case OP_SorterNext: { /* jump */
@@ -5145,7 +5158,8 @@ case OP_LoadAnalysis: {
**
** Remove the internal (in-memory) data structures that describe
** the table named P4 in database P1. This is called after a table
** is dropped in order to keep the internal representation of the
** is dropped from disk (using the Destroy opcode) in order to keep
** the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTable: {
@@ -5157,7 +5171,8 @@ case OP_DropTable: {
**
** Remove the internal (in-memory) data structures that describe
** the index named P4 in database P1. This is called after an index
** is dropped in order to keep the internal representation of the
** is dropped from disk (using the Destroy opcode)
** in order to keep the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropIndex: {
@@ -5169,7 +5184,8 @@ case OP_DropIndex: {
**
** Remove the internal (in-memory) data structures that describe
** the trigger named P4 in database P1. This is called after a trigger
** is dropped in order to keep the internal representation of the
** is dropped from disk (using the Destroy opcode) in order to keep
** the internal representation of the
** schema consistent with what is on disk.
*/
case OP_DropTrigger: {