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Enhance the JSONB lookup routine with logic to apply edits. The new logic is

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currently unused and hence untested but does not create any regressions.

FossilOrigin-Name: b12110276fc15d1b6b0cc455f89747ace7a09650d5ba433d8bb431bb4e5bc951
This commit is contained in:
drh
2023-11-03 12:09:22 +00:00
parent 24f7f5923d
commit 7b5123c796
3 changed files with 102 additions and 14 deletions
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102
src/json.c
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@@ -341,8 +341,19 @@ struct JsonParse {
u32 nBlob; /* Bytes of aBlob[] actually used */
u32 nBlobAlloc; /* Bytes allocated to aBlob[] */
u8 *aBlob; /* BLOB representation of zJson */
/* Search and edit information. See jsonLookupBlobStep() */
u8 eEdit; /* Edit operation to apply */
int delta; /* Size change due to the edit */
u32 nIns; /* Number of bytes to insert */
u8 *aIns; /* Content to be inserted */
};
/* Allowed values for JsonParse.eEdit */
#define JEDIT_DEL 0x01 /* Delete if exists */
#define JEDIT_INS 0x02 /* Insert if not exists */
#define JEDIT_REPL 0x04 /* Overwrite if exists */
#define JEDIT_SET 0x08 /* Insert or overwrite */
/*
** Maximum nesting depth of JSON for this implementation.
**
@@ -720,8 +731,6 @@ static void jsonAppendNormalizedReal(JsonString *p, const char *zIn, u32 N){
}
}
/*
** Append an sqlite3_value (such as a function parameter) to the JSON
** string under construction in p.
@@ -2558,6 +2567,31 @@ static int jsonBlobExpand(JsonParse *pParse, u32 N){
return 0;
}
/*
** If pParse->aBlob is not previously editable (because it is taken
** from sqlite3_value_blob(), as indicated by the fact that
** pParse->nBlobAlloc==0 and pParse->nBlob>0) then make it editable
** by making a copy into space obtained from malloc.
**
** Return true on success. Return false on OOM.
*/
static int jsonBlobMakeEditable(JsonParse *pParse){
u8 *aOld;
u32 nSize;
if( pParse->nBlobAlloc>0 ) return 1;
aOld = pParse->aBlob;
nSize = pParse->nBlob + pParse->nIns;
if( nSize>100 ) nSize -= 100;
pParse->aBlob = 0;
if( jsonBlobExpand(pParse, nSize) ){
return 0;
}
assert( pParse->nBlobAlloc >= pParse->nBlob + pParse->nIns );
memcpy(pParse->aBlob, aOld, pParse->nBlob);
return 1;
}
/* Expand pParse->aBlob and append N bytes.
**
** Return the number of errors.
@@ -3767,12 +3801,24 @@ static u32 jsonbArrayCount(JsonParse *pParse, u32 iRoot){
return k;
}
/*
** Edit the size of the element at iRoot by the amount in pParse->delta.
*/
static void jsonAfterEditSizeAdjust(JsonParse *pParse, u32 iRoot){
u32 sz;
assert( pParse->delta==0 );
(void)jsonbPayloadSize(pParse, iRoot, &sz);
sz += pParse->delta;
jsonBlobChangePayloadSize(pParse, iRoot, sz);
}
/*
** Error returns from jsonLookupBlobStep()
*/
#define JSON_BLOB_ERROR 0xffffffff
#define JSON_BLOB_NOTFOUND 0xfffffffe
#define JSON_BLOB_PATHERROR 0xfffffffd
#define JSON_BLOB_ISERROR(x) ((x)>=JSON_BLOB_PATHERROR)
/*
** Search along zPath to find the Json element specified. Return an
@@ -3785,12 +3831,39 @@ static u32 jsonLookupBlobStep(
u32 iRoot, /* Begin the search at this element of aBlob[] */
const char *zPath /* The path to search */
){
u32 i, j, k, nKey, sz, n, iEnd;
u32 i, j, k, nKey, sz, n, iEnd, rc;
const char *zKey;
u8 x;
if( pParse->oom ) return 0;
if( zPath[0]==0 ) return iRoot;
if( zPath[0]==0 ){
if( pParse->eEdit && jsonBlobMakeEditable(pParse) ){
n = jsonbPayloadSize(pParse, iRoot, &sz);
sz += n;
if( pParse->eEdit==JEDIT_DEL ){
memmove(&pParse->aBlob[iRoot], &pParse->aBlob[iRoot+sz],
pParse->nBlob - iRoot);
pParse->nBlob -= n;
pParse->delta = -(int)n;
}else if( pParse->eEdit==JEDIT_INS ){
/* Already exists, so json_insert() is a no-op */
}else{
/* json_set() or json_replace() */
int d = (int)pParse->nIns - (int)sz;
pParse->delta = d;
if( d!=0 ){
if( pParse->nBlob + d > pParse->nBlobAlloc ){
jsonBlobExpand(pParse, pParse->nBlob+d);
if( pParse->oom ) return iRoot;
}
memmove(&pParse->aBlob[iRoot+pParse->nIns],
&pParse->aBlob[iRoot+sz],
pParse->nBlob - iRoot - sz);
}
memcpy(&pParse->aBlob[iRoot], pParse->aIns, pParse->nIns);
}
}
return iRoot;
}
if( zPath[0]=='.' ){
x = pParse->aBlob[iRoot];
zPath++;
@@ -3828,7 +3901,9 @@ static u32 jsonLookupBlobStep(
if( ((pParse->aBlob[j])&0x0f)>JSONB_OBJECT ) return JSON_BLOB_ERROR;
n = jsonbPayloadSize(pParse, j, &sz);
if( n==0 || j+n+sz>iEnd ) return JSON_BLOB_ERROR;
return jsonLookupBlobStep(pParse, j, &zPath[i]);
rc = jsonLookupBlobStep(pParse, j, &zPath[i]);
if( pParse->delta ) jsonAfterEditSizeAdjust(pParse, iRoot);
return rc;
}
j = k+sz;
if( ((pParse->aBlob[j])&0x0f)>JSONB_OBJECT ) return JSON_BLOB_ERROR;
@@ -3872,7 +3947,9 @@ static u32 jsonLookupBlobStep(
iEnd = j+sz;
while( j<iEnd ){
if( k==0 ){
return jsonLookupBlobStep(pParse, j, &zPath[i+1]);
rc = jsonLookupBlobStep(pParse, j, &zPath[i+1]);
if( pParse->delta ) jsonAfterEditSizeAdjust(pParse, iRoot);
return rc;
}
k--;
n = jsonbPayloadSize(pParse, j, &sz);
@@ -3880,9 +3957,20 @@ static u32 jsonLookupBlobStep(
j += n+sz;
}
if( j>iEnd ) return JSON_BLOB_ERROR;
if( k>1 ) return JSON_BLOB_NOTFOUND;
}else{
return JSON_BLOB_PATHERROR;
}
if( pParse->eEdit==JEDIT_INS && jsonBlobMakeEditable(pParse) ){
assert( pParse->nBlob + pParse->nIns <= pParse->nBlobAlloc );
memmove(&pParse->aBlob[j], &pParse->aBlob[j+pParse->nIns],
pParse->nBlob - j);
memcpy(&pParse->aBlob[j], pParse->aIns, pParse->nIns);
pParse->delta = pParse->nIns;
pParse->nBlob += pParse->nIns;
jsonAfterEditSizeAdjust(pParse, iRoot);
return j;
}
return JSON_BLOB_NOTFOUND;
}