Experimental Physics and
Industrial Control System

Ben Franksen has proposed merging ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0.

Requested reviews:
  EPICS Core Developers (epics-core)

For more details, see:
https://code.launchpad.net/~bfrk/epics-base/+git/epics-base/+merge/396197

This is just refactors, no new features yet.
-- 
Your team EPICS Core Developers is requested to review the proposed merge of ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0.

diff --git a/modules/database/src/ioc/db/dbAccess.c b/modules/database/src/ioc/db/dbAccess.c
index d7e5d08..3f7554a 100644
--- a/modules/database/src/ioc/db/dbAccess.c
+++ b/modules/database/src/ioc/db/dbAccess.c
@@ -339,7 +339,7 @@ static void getOptions(DBADDR *paddr, char **poriginal, long *options,
         dbCommon        *pcommon;
         char            *pbuffer = *poriginal;
 
-        if (!pfl || pfl->type == dbfl_type_rec)
+        if (!pfl)
             field_type = paddr->field_type;
         else
             field_type = pfl->field_type;
@@ -349,7 +349,7 @@ static void getOptions(DBADDR *paddr, char **poriginal, long *options,
         if( (*options) & DBR_STATUS ) {
             unsigned short *pushort = (unsigned short *)pbuffer;
 
-            if (!pfl || pfl->type == dbfl_type_rec) {
+            if (!pfl) {
                 *pushort++ = pcommon->stat;
                 *pushort++ = pcommon->sevr;
             } else {
@@ -383,7 +383,7 @@ static void getOptions(DBADDR *paddr, char **poriginal, long *options,
         if( (*options) & DBR_TIME ) {
             epicsUInt32 *ptime = (epicsUInt32 *)pbuffer;
 
-            if (!pfl || pfl->type == dbfl_type_rec) {
+            if (!pfl) {
                 *ptime++ = pcommon->time.secPastEpoch;
                 *ptime++ = pcommon->time.nsec;
             } else {
@@ -904,22 +904,23 @@ long dbGet(DBADDR *paddr, short dbrType,
     if (nRequest && *nRequest == 0)
         return 0;
 
-    if (!pfl || pfl->type == dbfl_type_rec) {
+    if (!pfl) {
         field_type = paddr->field_type;
         no_elements = capacity = paddr->no_elements;
-
-        /* Update field info from record
-         * may modify paddr->pfield
-         */
-        if (paddr->pfldDes->special == SPC_DBADDR &&
-            (prset = dbGetRset(paddr)) &&
-            prset->get_array_info) {
-            status = prset->get_array_info(paddr, &no_elements, &offset);
-        } else
-            offset = 0;
     } else {
         field_type = pfl->field_type;
         no_elements = capacity = pfl->no_elements;
+    }
+
+    /* Update field info from record (if neccessary);
+     * may modify paddr->pfield.
+     */
+    if (!dbfl_has_copy(pfl) &&
+        paddr->pfldDes->special == SPC_DBADDR &&
+        (prset = dbGetRset(paddr)) &&
+        prset->get_array_info) {
+        status = prset->get_array_info(paddr, &no_elements, &offset);
+    } else {
         offset = 0;
     }
 
@@ -951,7 +952,7 @@ long dbGet(DBADDR *paddr, short dbrType,
             goto done;
         }
 
-        if (!pfl || pfl->type == dbfl_type_rec) {
+        if (!pfl) {
             status = dbFastGetConvertRoutine[field_type][dbrType]
                 (paddr->pfield, pbuf, paddr);
         } else {
@@ -964,6 +965,7 @@ long dbGet(DBADDR *paddr, short dbrType,
 
             localAddr.field_type = pfl->field_type;
             localAddr.field_size = pfl->field_size;
+            /* not used by dbFastConvert: */
             localAddr.no_elements = pfl->no_elements;
             if (pfl->type == dbfl_type_val)
                 localAddr.pfield = (char *) &pfl->u.v.field;
@@ -979,6 +981,8 @@ long dbGet(DBADDR *paddr, short dbrType,
         if (nRequest) {
             if (no_elements < *nRequest)
                 *nRequest = no_elements;
+            if (capacity < *nRequest)
+                *nRequest = capacity;
             n = *nRequest;
         } else {
             n = 1;
@@ -995,8 +999,8 @@ long dbGet(DBADDR *paddr, short dbrType,
         }
         /* convert data into the caller's buffer */
         if (n <= 0) {
-            ;/*do nothing*/
-        } else if (!pfl || pfl->type == dbfl_type_rec) {
+            ;                           /*do nothing */
+        } else if (!pfl) {
             status = convert(paddr, pbuf, n, capacity, offset);
         } else {
             DBADDR localAddr = *paddr; /* Structure copy */
@@ -1008,6 +1012,7 @@ long dbGet(DBADDR *paddr, short dbrType,
 
             localAddr.field_type = pfl->field_type;
             localAddr.field_size = pfl->field_size;
+            /* not used by dbConvert, it uses the passed capacity instead: */
             localAddr.no_elements = pfl->no_elements;
             if (pfl->type == dbfl_type_val)
                 localAddr.pfield = (char *) &pfl->u.v.field;
diff --git a/modules/database/src/ioc/db/dbChannel.c b/modules/database/src/ioc/db/dbChannel.c
index b6f53f7..c71d842 100644
--- a/modules/database/src/ioc/db/dbChannel.c
+++ b/modules/database/src/ioc/db/dbChannel.c
@@ -52,14 +52,12 @@ typedef struct parseContext {
 
 static void *dbChannelFreeList;
 static void *chFilterFreeList;
-static void *dbchStringFreeList;
 
 void dbChannelExit(void)
 {
     freeListCleanup(dbChannelFreeList);
     freeListCleanup(chFilterFreeList);
-    freeListCleanup(dbchStringFreeList);
-    dbChannelFreeList = chFilterFreeList = dbchStringFreeList = NULL;
+    dbChannelFreeList = chFilterFreeList = NULL;
 }
 
 void dbChannelInit (void)
@@ -69,7 +67,6 @@ void dbChannelInit (void)
 
     freeListInitPvt(&dbChannelFreeList,  sizeof(dbChannel), 128);
     freeListInitPvt(&chFilterFreeList,  sizeof(chFilter), 64);
-    freeListInitPvt(&dbchStringFreeList, sizeof(epicsOldString), 128);
     db_init_event_freelists();
 }
 
@@ -449,28 +446,6 @@ static long parseArrayRange(dbChannel* chan, const char *pname, const char **ppn
     return status;
 }
 
-/* Stolen from dbAccess.c: */
-static short mapDBFToDBR[DBF_NTYPES] =
-    {
-    /* DBF_STRING   => */DBR_STRING,
-    /* DBF_CHAR     => */DBR_CHAR,
-    /* DBF_UCHAR    => */DBR_UCHAR,
-    /* DBF_SHORT    => */DBR_SHORT,
-    /* DBF_USHORT   => */DBR_USHORT,
-    /* DBF_LONG     => */DBR_LONG,
-    /* DBF_ULONG    => */DBR_ULONG,
-    /* DBF_INT64    => */DBR_INT64,
-    /* DBF_UINT64   => */DBR_UINT64,
-    /* DBF_FLOAT    => */DBR_FLOAT,
-    /* DBF_DOUBLE   => */DBR_DOUBLE,
-    /* DBF_ENUM,    => */DBR_ENUM,
-    /* DBF_MENU,    => */DBR_ENUM,
-    /* DBF_DEVICE   => */DBR_ENUM,
-    /* DBF_INLINK   => */DBR_STRING,
-    /* DBF_OUTLINK  => */DBR_STRING,
-    /* DBF_FWDLINK  => */DBR_STRING,
-    /* DBF_NOACCESS => */DBR_NOACCESS };
-
 dbChannel * dbChannelCreate(const char *name)
 {
     const char *pname = name;
@@ -743,37 +718,24 @@ void dbChannelDelete(dbChannel *chan)
     freeListFree(dbChannelFreeList, chan);
 }
 
-static void freeArray(db_field_log *pfl) {
-    if (pfl->field_type == DBF_STRING && pfl->no_elements == 1) {
-        freeListFree(dbchStringFreeList, pfl->u.r.field);
-    } else {
-        free(pfl->u.r.field);
-    }
-}
-
-void dbChannelMakeArrayCopy(void *pvt, db_field_log *pfl, dbChannel *chan)
+/*
+ * Helper function to adjust no_elements, offset, and pfield
+ * when copying an array from a record.
+ */
+void dbChannelGetArrayInfo(dbChannel *chan,
+    void **pfield, long *no_elements, long *offset)
 {
-    void *p;
-    struct dbCommon *prec = dbChannelRecord(chan);
-
-    if (pfl->type != dbfl_type_rec) return;
-
-    pfl->type = dbfl_type_ref;
-    pfl->stat = prec->stat;
-    pfl->sevr = prec->sevr;
-    pfl->time = prec->time;
-    pfl->field_type  = chan->addr.field_type;
-    pfl->no_elements = chan->addr.no_elements;
-    pfl->field_size  = chan->addr.field_size;
-    pfl->u.r.dtor = freeArray;
-    pfl->u.r.pvt = pvt;
-    if (pfl->field_type == DBF_STRING && pfl->no_elements == 1) {
-        p = freeListCalloc(dbchStringFreeList);
-    } else {
-        p = calloc(pfl->no_elements, pfl->field_size);
+    rset *prset;
+    if (dbChannelSpecial(chan) == SPC_DBADDR &&
+        (prset = dbGetRset(&chan->addr)) &&
+        prset->get_array_info)
+    {
+        void *pfieldsave = dbChannelField(chan);
+        /* it is expected that this call always succeeds */
+        prset->get_array_info(&chan->addr, no_elements, offset);
+        *pfield = dbChannelField(chan);
+        dbChannelField(chan) = pfieldsave;
     }
-    if (p) dbGet(&chan->addr, mapDBFToDBR[pfl->field_type], p, NULL, &pfl->no_elements, NULL);
-    pfl->u.r.field = p;
 }
 
 /* FIXME: Do these belong in a different file? */
diff --git a/modules/database/src/ioc/db/dbChannel.h b/modules/database/src/ioc/db/dbChannel.h
index 1ca02bb..ec86e9e 100644
--- a/modules/database/src/ioc/db/dbChannel.h
+++ b/modules/database/src/ioc/db/dbChannel.h
@@ -65,8 +65,8 @@ typedef struct dbChannel {
 /* Prototype for the channel event function that is called in filter stacks
  *
  * When invoked the scan lock for the record associated with 'chan' _may_ be locked.
- * If pLog->type==dbfl_type_rec then dbScanLock() must be called before copying
- * data out of the associated record.
+ * Unless dbfl_has_copy(pLog), it must call dbScanLock before accessing the data,
+ * as this indicates the data is still owned by the record.
  *
  * This function has ownership of the field log pLog, if it wishes to discard
  * this update it should free the field log with db_delete_field_log() and
@@ -225,7 +225,8 @@ DBCORE_API void dbRegisterFilter(const char *key, const chFilterIf *fif, void *p
 DBCORE_API db_field_log* dbChannelRunPreChain(dbChannel *chan, db_field_log *pLogIn);
 DBCORE_API db_field_log* dbChannelRunPostChain(dbChannel *chan, db_field_log *pLogIn);
 DBCORE_API const chFilterPlugin * dbFindFilter(const char *key, size_t len);
-DBCORE_API void dbChannelMakeArrayCopy(void *pvt, db_field_log *pfl, dbChannel *chan);
+DBCORE_API void dbChannelGetArrayInfo(dbChannel *chan,
+        void **pfield, long *no_elements, long *offset);
 
 #ifdef __cplusplus
 }
diff --git a/modules/database/src/ioc/db/dbEvent.c b/modules/database/src/ioc/db/dbEvent.c
index 437cb6d..1db01f2 100644
--- a/modules/database/src/ioc/db/dbEvent.c
+++ b/modules/database/src/ioc/db/dbEvent.c
@@ -668,27 +668,21 @@ int db_post_extra_labor (dbEventCtx ctx)
     return DB_EVENT_OK;
 }
 
-/*
- *  DB_CREATE_EVENT_LOG()
- *
- *  NOTE: This assumes that the db scan lock is already applied
- *        (as it copies data from the record)
- */
-db_field_log* db_create_event_log (struct evSubscrip *pevent)
+static db_field_log* db_create_field_log (struct dbChannel *chan, int use_val)
 {
     db_field_log *pLog = (db_field_log *) freeListCalloc(dbevFieldLogFreeList);
 
     if (pLog) {
-        struct dbChannel *chan = pevent->chan;
         struct dbCommon  *prec = dbChannelRecord(chan);
-        pLog->ctx = dbfl_context_event;
-        if (pevent->useValque) {
+        pLog->stat = prec->stat;
+        pLog->sevr = prec->sevr;
+        pLog->time = prec->time;
+        pLog->field_type  = dbChannelFieldType(chan);
+        pLog->field_size  = dbChannelFieldSize(chan);
+        pLog->no_elements = dbChannelElements(chan);
+
+        if (use_val) {
             pLog->type = dbfl_type_val;
-            pLog->stat = prec->stat;
-            pLog->sevr = prec->sevr;
-            pLog->time = prec->time;
-            pLog->field_type  = dbChannelFieldType(chan);
-            pLog->no_elements = dbChannelElements(chan);
             /*
              * use memcpy to avoid a bus error on
              * union copy of char in the db at an odd
@@ -698,23 +692,46 @@ db_field_log* db_create_event_log (struct evSubscrip *pevent)
                    dbChannelField(chan),
                    dbChannelFieldSize(chan));
         } else {
-            pLog->type = dbfl_type_rec;
+            pLog->type = dbfl_type_ref;
+
+            /* don't make a copy yet, just reference the field value */
+            pLog->u.r.field = dbChannelField(chan);
+            /* indicate field value still owned by record */
+            pLog->u.r.dtor = NULL;
+            /* no private data yet, may be set by a filter */
+            pLog->u.r.pvt = NULL;
         }
     }
     return pLog;
 }
 
 /*
+ *  DB_CREATE_EVENT_LOG()
+ *
+ *  NOTE: This assumes that the db scan lock is already applied
+ *        (as it calls rset->get_array_info)
+ */
+db_field_log* db_create_event_log (struct evSubscrip *pevent)
+{
+    db_field_log *pLog = db_create_field_log(pevent->chan, pevent->useValque);
+    if (pLog) {
+        pLog->ctx  = dbfl_context_event;
+    }
+    return pLog;
+}
+
+/*
  *  DB_CREATE_READ_LOG()
  *
  */
 db_field_log* db_create_read_log (struct dbChannel *chan)
 {
-    db_field_log *pLog = (db_field_log *) freeListCalloc(dbevFieldLogFreeList);
-
+    db_field_log *pLog = db_create_field_log(chan,
+        dbChannelElements(chan) == 1 &&
+        dbChannelSpecial(chan) != SPC_DBADDR &&
+        dbChannelFieldSize(chan) <= sizeof(union native_value));
     if (pLog) {
         pLog->ctx  = dbfl_context_read;
-        pLog->type = dbfl_type_rec;
     }
     return pLog;
 }
@@ -738,20 +755,6 @@ static void db_queue_event_log (evSubscrip *pevent, db_field_log *pLog)
     LOCKEVQUE (ev_que);
 
     /*
-     * if we have an event on the queue and both the last
-     * event on the queue and the current event are emtpy
-     * (i.e. of type dbfl_type_rec), simply ignore duplicate
-     * events (saving empty events serves no purpose)
-     */
-    if (pevent->npend > 0u &&
-        (*pevent->pLastLog)->type == dbfl_type_rec &&
-        pLog->type == dbfl_type_rec) {
-        db_delete_field_log(pLog);
-        UNLOCKEVQUE (ev_que);
-        return;
-    }
-
-    /*
      * add to task local event que
      */
 
diff --git a/modules/database/src/ioc/db/dbExtractArray.c b/modules/database/src/ioc/db/dbExtractArray.c
index a7dcf4d..197e66c 100644
--- a/modules/database/src/ioc/db/dbExtractArray.c
+++ b/modules/database/src/ioc/db/dbExtractArray.c
@@ -14,11 +14,12 @@
 /*
  *  Author: Ralph Lange <Ralph.Lange at bessy.de>
  *
- *  based on dbConvert.c
+ *  based on dbConvert.c, see copyNoConvert
  *  written by: Bob Dalesio, Marty Kraimer
  */
 
 #include <string.h>
+#include <assert.h>
 
 #include "epicsTypes.h"
 
@@ -26,61 +27,30 @@
 #include "dbAddr.h"
 #include "dbExtractArray.h"
 
-void dbExtractArrayFromRec(const dbAddr *paddr, void *pto,
-                           long nRequest, long no_elements, long offset, long increment)
+void dbExtractArray(const void *pfrom, void *pto, short field_size,
+    long nRequest, long no_elements, long offset, long increment)
 {
     char *pdst = (char *) pto;
-    char *psrc = (char *) paddr->pfield;
-    long nUpperPart;
-    int i;
-    short srcSize = paddr->field_size;
-    short dstSize = srcSize;
-    char isString = (paddr->field_type == DBF_STRING);
+    const char *psrc = (char *) pfrom;
 
-    if (nRequest > no_elements) nRequest = no_elements;
-    if (isString && srcSize > MAX_STRING_SIZE) dstSize = MAX_STRING_SIZE;
+    /* assert preconditions */
+    assert(nRequest >= 0);
+    assert(no_elements >= 0);
+    assert(increment > 0);
+    assert(0 <= offset);
+    assert(offset < no_elements);
 
-    if (increment == 1 && dstSize == srcSize) {
-        nUpperPart = nRequest < no_elements - offset ? nRequest : no_elements - offset;
-        memcpy(pdst, &psrc[offset * srcSize], dstSize * nUpperPart);
+    if (increment == 1) {
+        long nUpperPart =
+            nRequest < no_elements - offset ? nRequest : no_elements - offset;
+        memcpy(pdst, psrc + (offset * field_size), field_size * nUpperPart);
         if (nRequest > nUpperPart)
-            memcpy(&pdst[dstSize * nUpperPart], psrc, dstSize * (nRequest - nUpperPart));
-        if (isString)
-            for (i = 1; i <= nRequest; i++)
-                pdst[dstSize*i-1] = '\0';
+            memcpy(pdst + (field_size * nUpperPart), psrc,
+                field_size * (nRequest - nUpperPart));
     } else {
-        for (; nRequest > 0; nRequest--, pdst += dstSize, offset += increment) {
+        for (; nRequest > 0; nRequest--, pdst += field_size, offset += increment) {
             offset %= no_elements;
-            memcpy(pdst, &psrc[offset*srcSize], dstSize);
-            if (isString) pdst[dstSize-1] = '\0';
-        }
-    }
-}
-
-void dbExtractArrayFromBuf(const void *pfrom, void *pto,
-                           short field_size, short field_type,
-                           long nRequest, long no_elements, long offset, long increment)
-{
-    char *pdst = (char *) pto;
-    char *psrc = (char *) pfrom;
-    int i;
-    short srcSize = field_size;
-    short dstSize = srcSize;
-    char isString = (field_type == DBF_STRING);
-
-    if (nRequest > no_elements) nRequest = no_elements;
-    if (offset > no_elements - 1) offset = no_elements - 1;
-    if (isString && dstSize >= MAX_STRING_SIZE) dstSize = MAX_STRING_SIZE - 1;
-
-    if (increment == 1) {
-        memcpy(pdst, &psrc[offset * srcSize], dstSize * nRequest);
-        if (isString)
-            for (i = 1; i <= nRequest; i++)
-                pdst[dstSize*i] = '\0';
-    } else {
-        for (; nRequest > 0; nRequest--, pdst += srcSize, offset += increment) {
-            memcpy(pdst, &psrc[offset*srcSize], dstSize);
-            if (isString) pdst[dstSize] = '\0';
+            memcpy(pdst, psrc + (offset * field_size), field_size);
         }
     }
 }
diff --git a/modules/database/src/ioc/db/dbExtractArray.h b/modules/database/src/ioc/db/dbExtractArray.h
index b44bd15..9755ac5 100644
--- a/modules/database/src/ioc/db/dbExtractArray.h
+++ b/modules/database/src/ioc/db/dbExtractArray.h
@@ -22,11 +22,36 @@
 extern "C" {
 #endif
 
-epicsShareFunc void dbExtractArrayFromRec(const DBADDR *paddr, void *pto,
-                                          long nRequest, long no_elements, long offset, long increment);
-epicsShareFunc void dbExtractArrayFromBuf(const void *pfrom, void *pto,
-                                          short field_size, short field_type,
-                                          long nRequest, long no_elements, long offset, long increment);
+/** @brief Make a copy of parts of an array.
+ *
+ * The source array may or may not be a record field.
+ *
+ * The increment parameter is used to support array filters; it
+ * means: copy only every increment'th element, starting at offset.
+ *
+ * The offset and no_elements parameters are used to support the
+ * circular buffer feature of record fields: elements before offset
+ * are treated as if they came right after no_elements.
+ *
+ * This function does not do any conversion on the array elements.
+ *
+ * Preconditions:
+ *   nRequest >= 0, no_elements >= 0, increment > 0
+ *   0 <= offset < no_elements
+ *   pto points to a buffer with at least field_size*nRequest bytes
+ *   pfrom points to a buffer with exactly field_size*no_elements bytes
+ *
+ * @param pfrom         Pointer to source array.
+ * @param pto           Pointer to target array.
+ * @param field_size    Size of an array element.
+ * @param nRequest      Number of elements to copy.
+ * @param no_elements   Number of elements in source array.
+ * @param offset        Wrap-around point in source array.
+ * @param increment     Copy only every increment'th element.
+ */
+epicsShareFunc void dbExtractArray(const void *pfrom, void *pto,
+    short field_size, long nRequest, long no_elements, long offset,
+    long increment);
 
 #ifdef __cplusplus
 }
diff --git a/modules/database/src/ioc/db/db_field_log.h b/modules/database/src/ioc/db/db_field_log.h
index 5a40f5f..222bad0 100644
--- a/modules/database/src/ioc/db/db_field_log.h
+++ b/modules/database/src/ioc/db/db_field_log.h
@@ -57,20 +57,31 @@ union native_value {
 struct db_field_log;
 typedef void (dbfl_freeFunc)(struct db_field_log *pfl);
 
-/* Types of db_field_log: rec = use record, val = val inside, ref = reference inside */
+/*
+ * A db_field_log has one of two types:
+ *
+ * dbfl_type_ref - Reference to value
+ *  Used for variable size (array) data types.  Meta-data
+ *  is stored in the field log, but value data is stored externally.
+ *  Only the dbfl_ref side of the data union is valid.
+ *
+ * dbfl_type_val - Internal value
+ *  Used to store small scalar data.  Meta-data and value are
+ *  present in this structure and no external references are used.
+ *  Only the dbfl_val side of the data union is valid.
+ */
 typedef enum dbfl_type {
-    dbfl_type_rec = 0,
     dbfl_type_val,
     dbfl_type_ref
 } dbfl_type;
 
 /* Context of db_field_log: event = subscription update, read = read reply */
 typedef enum dbfl_context {
-    dbfl_context_read = 0,
+    dbfl_context_read,
     dbfl_context_event
 } dbfl_context;
 
-#define dbflTypeStr(t) (t==dbfl_type_val?"val":t==dbfl_type_rec?"rec":"ref")
+#define dbflTypeStr(t) (t==dbfl_type_val?"val":"ref")
 
 struct dbfl_val {
     union native_value field; /* Field value */
@@ -82,6 +93,8 @@ struct dbfl_val {
  * db_delete_field_log().  Any code which changes a dbfl_type_ref
  * field log to another type, or to reference different data,
  * must explicitly call the dtor function.
+ * If the dtor is NULL and no_elements > 0, then this means the array
+ * data is still owned by a record. See the macro dbfl_has_copy below.
  */
 struct dbfl_ref {
     dbfl_freeFunc     *dtor;  /* Callback to free filter-allocated resources */
@@ -89,8 +102,11 @@ struct dbfl_ref {
     void              *field; /* Field value */
 };
 
+/*
+ * Note that field_size may be larger than MAX_STRING_SIZE.
+ */
 typedef struct db_field_log {
-    unsigned int     type:2;  /* type (union) selector */
+    unsigned int     type:1;  /* type (union) selector */
     /* ctx is used for all types */
     unsigned int      ctx:1;  /* context (operation type) */
     /* the following are used for value and reference types */
@@ -98,8 +114,8 @@ typedef struct db_field_log {
     unsigned short     stat;  /* Alarm Status */
     unsigned short     sevr;  /* Alarm Severity */
     short        field_type;  /* DBF type of data */
-    short        field_size;  /* Data size */
-    long        no_elements;  /* No of array elements */
+    short        field_size;  /* Size of a single element */
+    long        no_elements;  /* No of valid array elements */
     union {
         struct dbfl_val v;
         struct dbfl_ref r;
@@ -107,27 +123,16 @@ typedef struct db_field_log {
 } db_field_log;
 
 /*
- * A db_field_log will in one of three types:
- *
- * dbfl_type_rec - Reference to record
- *  The field log stores no data itself.  Data must instead be taken
- *  via the dbChannel* which must always be provided when along
- *  with the field log.
- *  For this type only the 'type' and 'ctx' members are used.
- *
- * dbfl_type_ref - Reference to outside value
- *  Used for variable size (array) data types.  Meta-data
- *  is stored in the field log, but value data is stored externally
- *  (see struct dbfl_ref).
- *  For this type all meta-data members are used.  The dbfl_ref side of the
- *  data union is used.
- *
- * dbfl_type_val - Internal value
- *  Used to store small scalar data.  Meta-data and value are
- *  present in this structure and no external references are used.
- *  For this type all meta-data members are used.  The dbfl_val side of the
- *  data union is used.
+ * Whether a db_field_log* owns the field data. If this is the case, then the
+ * db_field_log is fully decoupled from the record: there is no need to lock
+ * the record when accessing the data, nor to call any rset methods (like
+ * get_array_info) because this has already been done when we made the copy. A
+ * special case here is that of no (remaining) data (i.e. no_elements==0). In
+ * this case, making a copy is redundant, so we have no dtor. But conceptually
+ * the db_field_log still owns the (empty) data.
  */
+#define dbfl_has_copy(p)\
+ ((p) && ((p)->type==dbfl_type_val || (p)->u.r.dtor || (p)->no_elements==0))
 
 #ifdef __cplusplus
 }
diff --git a/modules/database/src/std/filters/arr.c b/modules/database/src/std/filters/arr.c
index 8138480..5f25184 100644
--- a/modules/database/src/std/filters/arr.c
+++ b/modules/database/src/std/filters/arr.c
@@ -13,16 +13,14 @@
 
 #include <stdio.h>
 
-#include <freeList.h>
-#include <dbAccess.h>
-#include <dbExtractArray.h>
-#include <db_field_log.h>
-#include <dbLock.h>
-#include <recSup.h>
-#include <epicsExit.h>
-#include <special.h>
-#include <chfPlugin.h>
-#include <epicsExport.h>
+#include "chfPlugin.h"
+#include "dbAccessDefs.h"
+#include "dbExtractArray.h"
+#include "db_field_log.h"
+#include "dbLock.h"
+#include "epicsExit.h"
+#include "freeList.h"
+#include "epicsExport.h"
 
 typedef struct myStruct {
     epicsInt32 start;
@@ -46,6 +44,8 @@ static void * allocPvt(void)
     myStruct *my = (myStruct*) freeListCalloc(myStructFreeList);
     if (!my) return NULL;
 
+    /* defaults */
+    my->start = 0;
     my->incr = 1;
     my->end = -1;
     return (void *) my;
@@ -77,8 +77,6 @@ static void freeArray(db_field_log *pfl)
 static long wrapArrayIndices(long *start, const long increment, long *end,
     const long no_elements)
 {
-    long len = 0;
-
     if (*start < 0) *start = no_elements + *start;
     if (*start < 0) *start = 0;
     if (*start > no_elements) *start = no_elements;
@@ -87,85 +85,65 @@ static long wrapArrayIndices(long *start, const long increment, long *end,
     if (*end < 0) *end = 0;
     if (*end >= no_elements) *end = no_elements - 1;
 
-    if (*end - *start >= 0) len = 1 + (*end - *start) / increment;
-    return len;
+    if (*end - *start >= 0)
+        return 1 + (*end - *start) / increment;
+    else
+        return 0;
 }
 
 static db_field_log* filter(void* pvt, dbChannel *chan, db_field_log *pfl)
 {
     myStruct *my = (myStruct*) pvt;
-    struct dbCommon *prec;
-    rset *prset;
+    int must_lock;
     long start = my->start;
     long end = my->end;
-    long nTarget = 0;
+    long nTarget;
+    void *pTarget;
     long offset = 0;
-    long nSource = dbChannelElements(chan);
-    long capacity = nSource;
-    void *pdst;
+    long nSource = pfl->no_elements;
+    void *pSource = pfl->u.r.field;
 
     switch (pfl->type) {
     case dbfl_type_val:
-        /* Only filter arrays */
-        break;
-
-    case dbfl_type_rec:
-        /* Extract from record */
-        if (dbChannelSpecial(chan) == SPC_DBADDR &&
-            nSource > 1 &&
-            (prset = dbGetRset(&chan->addr)) &&
-            prset->get_array_info)
-        {
-            void *pfieldsave = dbChannelField(chan);
-            prec = dbChannelRecord(chan);
-            dbScanLock(prec);
-            prset->get_array_info(&chan->addr, &nSource, &offset);
-            nTarget = wrapArrayIndices(&start, my->incr, &end, nSource);
-            pfl->type = dbfl_type_ref;
-            pfl->stat = prec->stat;
-            pfl->sevr = prec->sevr;
-            pfl->time = prec->time;
-            pfl->field_type = dbChannelFieldType(chan);
-            pfl->field_size = dbChannelFieldSize(chan);
-            pfl->no_elements = nTarget;
-            if (nTarget) {
-                pdst = freeListCalloc(my->arrayFreeList);
-                if (pdst) {
-                    pfl->u.r.dtor = freeArray;
-                    pfl->u.r.pvt = my->arrayFreeList;
-                    offset = (offset + start) % dbChannelElements(chan);
-                    dbExtractArrayFromRec(&chan->addr, pdst, nTarget, capacity,
-                        offset, my->incr);
-                    pfl->u.r.field = pdst;
-                }
-            }
-            dbScanUnlock(prec);
-            dbChannelField(chan) = pfieldsave;
-        }
+        /* TODO Treat scalars as arrays with 1 element */
         break;
 
-    /* Extract from buffer */
     case dbfl_type_ref:
-        pdst = NULL;
-        nSource = pfl->no_elements;
-        nTarget = wrapArrayIndices(&start, my->incr, &end, nSource);
-        pfl->no_elements = nTarget;
-        if (nTarget) {
-            /* Copy the data out */
-            void *psrc = pfl->u.r.field;
-
-            pdst = freeListCalloc(my->arrayFreeList);
-            if (!pdst) break;
-            offset = start;
-            dbExtractArrayFromBuf(psrc, pdst, pfl->field_size, pfl->field_type,
-                nTarget, nSource, offset, my->incr);
+        must_lock = !pfl->u.r.dtor;
+        if (must_lock) {
+            dbScanLock(dbChannelRecord(chan));
+            dbChannelGetArrayInfo(chan, &pSource, &nSource, &offset);
         }
-        if (pfl->u.r.dtor) pfl->u.r.dtor(pfl);
-        if (nTarget) {
+        nTarget = wrapArrayIndices(&start, my->incr, &end, nSource);
+        if (nTarget > 0) {
+            /* copy the data */
+            pTarget = freeListCalloc(my->arrayFreeList);
+            if (!pTarget) break;
+            /* must do the wrap-around with the original no_elements */
+            offset = (offset + start) % pfl->no_elements;
+            dbExtractArray(pSource, pTarget, pfl->field_size,
+                nTarget, pfl->no_elements, offset, my->incr);
+            if (pfl->u.r.dtor) pfl->u.r.dtor(pfl);
+            pfl->u.r.field = pTarget;
             pfl->u.r.dtor = freeArray;
             pfl->u.r.pvt = my->arrayFreeList;
-            pfl->u.r.field = pdst;
         }
+        /* Adjust no_elements to refer to the new pTarget.
+         *
+         * Setting pfl->no_elements outside of the "if" clause above is
+         * done to make requests fail if nTarget is zero, that is, if all
+         * elements selected by the filter are outside the array bounds.
+         * TODO:
+         * It would be possible to lift this restriction by interpreting
+         * a request with *no* number of elements (NULL pointer) as scalar
+         * (meaning: fail if we get less than one element); in contrast,
+         * a request that explicitly specifies one element would be
+         * interpreted as an array request, for which zero elements would
+         * be a normal expected result.
+         */
+        pfl->no_elements = nTarget;
+        if (must_lock)
+            dbScanUnlock(dbChannelRecord(chan));
         break;
     }
     return pfl;
diff --git a/modules/database/src/std/filters/ts.c b/modules/database/src/std/filters/ts.c
index 8a07c3f..0feadb0 100644
--- a/modules/database/src/std/filters/ts.c
+++ b/modules/database/src/std/filters/ts.c
@@ -12,21 +12,44 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
-#include <chfPlugin.h>
-#include <dbLock.h>
-#include <db_field_log.h>
-#include <epicsExport.h>
+#include "chfPlugin.h"
+#include "db_field_log.h"
+#include "dbExtractArray.h"
+#include "dbLock.h"
+#include "epicsExport.h"
+
+/*
+ * The size of the data is different for each channel, and can even
+ * change at runtime, so a freeList doesn't make much sense here.
+ */
+static void freeArray(db_field_log *pfl) {
+    free(pfl->u.r.field);
+}
 
 static db_field_log* filter(void* pvt, dbChannel *chan, db_field_log *pfl) {
     epicsTimeStamp now;
     epicsTimeGetCurrent(&now);
 
-    /* If string or array, must make a copy (to ensure coherence between time and data) */
-    if (pfl->type == dbfl_type_rec) {
-        dbScanLock(dbChannelRecord(chan));
-        dbChannelMakeArrayCopy(pvt, pfl, chan);
-        dbScanUnlock(dbChannelRecord(chan));
+    /* If reference and not already copied,
+       must make a copy (to ensure coherence between time and data) */
+    if (pfl->type == dbfl_type_ref && !pfl->u.r.dtor) {
+        void *pTarget = calloc(pfl->no_elements, pfl->field_size);
+        void *pSource = pfl->u.r.field;
+        if (pTarget) {
+            long offset = 0;
+            long nSource = pfl->no_elements;
+            dbScanLock(dbChannelRecord(chan));
+            dbChannelGetArrayInfo(chan, &pSource, &nSource, &offset);
+            dbExtractArray(pSource, pTarget, pfl->field_size,
+                nSource, pfl->no_elements, offset, 1);
+            pfl->u.r.field = pTarget;
+            pfl->u.r.dtor = freeArray;
+            pfl->u.r.pvt = pvt;
+            dbScanUnlock(dbChannelRecord(chan));
+        }
     }
 
     pfl->time = now;
diff --git a/modules/database/test/ioc/db/dbChArrTest.cpp b/modules/database/test/ioc/db/dbChArrTest.cpp
index 90702b5..9965852 100644
--- a/modules/database/test/ioc/db/dbChArrTest.cpp
+++ b/modules/database/test/ioc/db/dbChArrTest.cpp
@@ -131,7 +131,7 @@ static void check(short dbr_type) {
     memset(buf, 0, sizeof(buf)); \
     (void) dbPutField(&offaddr, DBR_LONG, &off, 1); \
     pfl = db_create_read_log(pch); \
-    testOk(pfl && pfl->type == dbfl_type_rec, "Valid pfl, type = rec"); \
+    testOk(pfl && pfl->type == dbfl_type_ref, "Valid pfl, type = ref"); \
     testOk(!dbChannelGetField(pch, DBR_LONG, buf, NULL, &req, pfl), "Got Field value"); \
     testOk(req == Size, "Got %ld elements (expected %d)", req, Size); \
     if (!testOk(!memcmp(buf, Expected, sizeof(Expected)), "Data correct")) \
diff --git a/modules/database/test/std/filters/arrTest.cpp b/modules/database/test/std/filters/arrTest.cpp
index bd83bd8..dfbbf46 100644
--- a/modules/database/test/std/filters/arrTest.cpp
+++ b/modules/database/test/std/filters/arrTest.cpp
@@ -73,9 +73,9 @@ static int fl_equals_array(short type, const db_field_log *pfl1, void *p2) {
             }
             break;
         case DBR_STRING:
-            if (strtol(&((const char*)pfl1->u.r.field)[i*MAX_STRING_SIZE], NULL, 0) != ((epicsInt32*)p2)[i]) {
+            if (strtol(&((const char*)pfl1->u.r.field)[i*pfl1->field_size], NULL, 0) != ((epicsInt32*)p2)[i]) {
                 testDiag("at index=%d: field log has '%s', should be '%d'",
-                         i, &((const char*)pfl1->u.r.field)[i*MAX_STRING_SIZE], ((epicsInt32*)p2)[i]);
+                         i, &((const char*)pfl1->u.r.field)[i*pfl1->field_size], ((epicsInt32*)p2)[i]);
                 return 0;
             }
             break;
@@ -120,7 +120,7 @@ static void testHead (const char *title, const char *typ = "") {
     off = Offset; \
     (void) dbPutField(&offaddr, DBR_LONG, &off, 1); \
     pfl = db_create_read_log(pch); \
-    testOk(pfl->type == dbfl_type_rec, "original field log has type rec"); \
+    testOk(pfl->type == dbfl_type_ref, "original field log has type ref"); \
     pfl2 = dbChannelRunPostChain(pch, pfl); \
     testOk(pfl2 == pfl, "call does not drop or replace field_log"); \
     testOk(pfl->type == dbfl_type_ref, "filtered field log has type ref"); \
diff --git a/modules/database/test/std/filters/dbndTest.c b/modules/database/test/std/filters/dbndTest.c
index e7897e2..0206865 100644
--- a/modules/database/test/std/filters/dbndTest.c
+++ b/modules/database/test/std/filters/dbndTest.c
@@ -130,7 +130,7 @@ MAIN(dbndTest)
     dbEventCtx evtctx;
     int logsFree, logsFinal;
 
-    testPlan(77);
+    testPlan(72);
 
     testdbPrepare();
 
@@ -171,12 +171,9 @@ MAIN(dbndTest)
            "dbnd has one filter with argument in pre chain");
     testOk((ellCount(&pch->post_chain) == 0), "dbnd has no filter in post chain");
 
-    /* Field logs of type ref and rec: pass any update */
-
-    testHead("Field logs of type ref and rec");
-    fl1.type = dbfl_type_rec;
-    mustPassTwice(pch, &fl1, "abs field_log=rec", 0., 0);
+    /* Field logs of type ref: pass any update */
 
+    testHead("Field logs of type ref");
     fl1.type = dbfl_type_ref;
     mustPassTwice(pch, &fl1, "abs field_log=ref", 0., 0);
 

Replies:

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 mdavidsaver via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

Re: [Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 Ben Franksen via Core-talk

[Merge] ~bfrk/epics-base:remove-dbfl_type_rec into epics-base:7.0 noreply--- via Core-talk

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