Adding upstream version 2:4.0.4.upstream/2%4.0.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1027 insertions, 0 deletions

diff --git a/library/diskstats.c b/library/diskstats.c
new file mode 100644
index 0000000..b4e41f3
--- /dev/null
+++ b/library/diskstats.c
@@ -0,0 +1,1027 @@
+/*
+ * diskstats.c - disk I/O related definitions for libproc2
+ *
+ * Copyright © 2015-2023 Craig Small <csmall@dropbear.xyz>
+ * Copyright © 2015-2023 Jim Warner <james.warner@comcast.net>
+ * Copyright © 2003      Albert Cahalan
+ * Copyright © 2003      Fabian Frederick
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "procps-private.h"
+#include "diskstats.h"
+
+/* The following define will cause the 'node_add' function to maintain our |
+   nodes list in ascending alphabetical order which could be used to avoid |
+   a sort on name. Without it, we default to a 'pull-up' stack at slightly |
+   more effort than a simple 'push-down' list to duplicate prior behavior. | */
+//#define ALPHABETIC_NODES
+
+#define DISKSTATS_LINE_LEN  1024
+#define DISKSTATS_NAME_LEN  34
+#define DISKSTATS_FILE      "/proc/diskstats"
+#define SYSBLOCK_DIR        "/sys/block"
+
+#define STACKS_INCR         64           // amount reap stack allocations grow
+#define STR_COMPARE         strverscmp
+
+/* ----------------------------------------------------------------------- +
+   this provision can help ensure that our Item_table remains synchronized |
+   with the enumerators found in the associated header file. It's intended |
+   to only be used locally (& temporarily) at some point before a release! | */
+// #define ITEMTABLE_DEBUG //--------------------------------------------- |
+// ----------------------------------------------------------------------- +
+
+
+struct dev_data {
+    unsigned long reads;
+    unsigned long reads_merged;
+    unsigned long read_sectors;
+    unsigned long read_time;
+    unsigned long writes;
+    unsigned long writes_merged;
+    unsigned long write_sectors;
+    unsigned long write_time;
+    unsigned long io_inprogress;
+    unsigned long io_time;
+    unsigned long io_wtime;
+};
+
+struct dev_node {
+    char name[DISKSTATS_NAME_LEN+1];
+    int type;
+    int major;
+    int minor;
+    time_t stamped;
+    struct dev_data new;
+    struct dev_data old;
+    struct dev_node *next;
+};
+
+struct stacks_extent {
+    int ext_numstacks;
+    struct stacks_extent *next;
+    struct diskstats_stack **stacks;
+};
+
+struct ext_support {
+    int numitems;                      // includes 'logical_end' delimiter
+    enum diskstats_item *items;        // includes 'logical_end' delimiter
+    struct stacks_extent *extents;     // anchor for these extents
+};
+
+struct fetch_support {
+    struct diskstats_stack **anchor;   // fetch consolidated extents
+    int n_alloc;                       // number of above pointers allocated
+    int n_inuse;                       // number of above pointers occupied
+    int n_alloc_save;                  // last known reap.stacks allocation
+    struct diskstats_reaped results;   // count + stacks for return to caller
+};
+
+struct diskstats_info {
+    int refcount;
+    FILE *diskstats_fp;
+    time_t old_stamp;                  // previous read seconds
+    time_t new_stamp;                  // current read seconds
+    struct dev_node *nodes;            // dev nodes anchor
+    struct ext_support select_ext;     // supports concurrent select/reap
+    struct ext_support fetch_ext;      // supports concurrent select/reap
+    struct fetch_support fetch;        // support for procps_diskstats_reap
+    struct diskstats_result get_this;  // used by procps_diskstats_get
+};
+
+
+// ___ Results 'Set' Support ||||||||||||||||||||||||||||||||||||||||||||||||||
+
+#define setNAME(e) set_diskstats_ ## e
+#define setDECL(e) static void setNAME(e) \
+    (struct diskstats_result *R, struct dev_node *N)
+
+// regular assignment
+#define DEV_set(e,t,x) setDECL(e) { R->result. t = N-> x; }
+#define REG_set(e,t,x) setDECL(e) { R->result. t = N->new. x; }
+// delta assignment
+#define HST_set(e,t,x) setDECL(e) { R->result. t = ( N->new. x - N->old. x ); }
+
+setDECL(noop)  { (void)R; (void)N; }
+setDECL(extra) { (void)N; R->result.ul_int = 0; }
+
+DEV_set(NAME,                 str,     name)
+DEV_set(TYPE,                 s_int,   type)
+DEV_set(MAJOR,                s_int,   major)
+DEV_set(MINOR,                s_int,   minor)
+
+REG_set(READS,                ul_int,  reads)
+REG_set(READS_MERGED,         ul_int,  reads_merged)
+REG_set(READ_SECTORS,         ul_int,  read_sectors)
+REG_set(READ_TIME,            ul_int,  read_time)
+REG_set(WRITES,               ul_int,  writes)
+REG_set(WRITES_MERGED,        ul_int,  writes_merged)
+REG_set(WRITE_SECTORS,        ul_int,  write_sectors)
+REG_set(WRITE_TIME,           ul_int,  write_time)
+REG_set(IO_TIME,              ul_int,  io_time)
+REG_set(WEIGHTED_TIME,        ul_int,  io_wtime)
+
+REG_set(IO_INPROGRESS,        s_int,   io_inprogress)
+
+HST_set(DELTA_READS,          s_int,   reads)
+HST_set(DELTA_READS_MERGED,   s_int,   reads_merged)
+HST_set(DELTA_READ_SECTORS,   s_int,   read_sectors)
+HST_set(DELTA_READ_TIME,      s_int,   read_time)
+HST_set(DELTA_WRITES,         s_int,   writes)
+HST_set(DELTA_WRITES_MERGED,  s_int,   writes_merged)
+HST_set(DELTA_WRITE_SECTORS,  s_int,   write_sectors)
+HST_set(DELTA_WRITE_TIME,     s_int,   write_time)
+HST_set(DELTA_IO_TIME,        s_int,   io_time)
+HST_set(DELTA_WEIGHTED_TIME,  s_int,   io_wtime)
+
+#undef setDECL
+#undef DEV_set
+#undef REG_set
+#undef HST_set
+
+
+// ___ Sorting Support ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
+
+struct sort_parms {
+    int offset;
+    enum diskstats_sort_order order;
+};
+
+#define srtNAME(t) sort_diskstats_ ## t
+#define srtDECL(t) static int srtNAME(t) \
+    (const struct diskstats_stack **A, const struct diskstats_stack **B, struct sort_parms *P)
+
+srtDECL(s_int) {
+    const struct diskstats_result *a = (*A)->head + P->offset; \
+    const struct diskstats_result *b = (*B)->head + P->offset; \
+    return P->order * (a->result.s_int - b->result.s_int);
+}
+
+srtDECL(ul_int) {
+    const struct diskstats_result *a = (*A)->head + P->offset; \
+    const struct diskstats_result *b = (*B)->head + P->offset; \
+    if ( a->result.ul_int > b->result.ul_int ) return P->order > 0 ?  1 : -1; \
+    if ( a->result.ul_int < b->result.ul_int ) return P->order > 0 ? -1 :  1; \
+    return 0;
+}
+
+srtDECL(str) {
+    const struct diskstats_result *a = (*A)->head + P->offset;
+    const struct diskstats_result *b = (*B)->head + P->offset;
+    return P->order * STR_COMPARE(a->result.str, b->result.str);
+}
+
+srtDECL(noop) { \
+    (void)A; (void)B; (void)P; \
+    return 0;
+}
+
+#undef srtDECL
+
+
+// ___ Controlling Table ||||||||||||||||||||||||||||||||||||||||||||||||||||||
+
+typedef void (*SET_t)(struct diskstats_result *, struct dev_node *);
+#ifdef ITEMTABLE_DEBUG
+#define RS(e) (SET_t)setNAME(e), DISKSTATS_ ## e, STRINGIFY(DISKSTATS_ ## e)
+#else
+#define RS(e) (SET_t)setNAME(e)
+#endif
+
+typedef int  (*QSR_t)(const void *, const void *, void *);
+#define QS(t) (QSR_t)srtNAME(t)
+
+#define TS(t) STRINGIFY(t)
+#define TS_noop ""
+
+        /*
+         * Need it be said?
+         * This table must be kept in the exact same order as
+         * those *enum diskstats_item* guys ! */
+static struct {
+    SET_t setsfunc;              // the actual result setting routine
+#ifdef ITEMTABLE_DEBUG
+    int   enumnumb;              // enumerator (must match position!)
+    char *enum2str;              // enumerator name as a char* string
+#endif
+    QSR_t sortfunc;              // sort cmp func for a specific type
+    char *type2str;              // the result type as a string value
+} Item_table[] = {
+/*  setsfunc                  sortfunc     type2str
+    ------------------------  -----------  ---------- */
+  { RS(noop),                 QS(noop),    TS_noop    },
+  { RS(extra),                QS(ul_int),  TS_noop    },
+
+  { RS(NAME),                 QS(str),     TS(str)    },
+  { RS(TYPE),                 QS(s_int),   TS(s_int)  },
+  { RS(MAJOR),                QS(s_int),   TS(s_int)  },
+  { RS(MINOR),                QS(s_int),   TS(s_int)  },
+
+  { RS(READS),                QS(ul_int),  TS(ul_int) },
+  { RS(READS_MERGED),         QS(ul_int),  TS(ul_int) },
+  { RS(READ_SECTORS),         QS(ul_int),  TS(ul_int) },
+  { RS(READ_TIME),            QS(ul_int),  TS(ul_int) },
+  { RS(WRITES),               QS(ul_int),  TS(ul_int) },
+  { RS(WRITES_MERGED),        QS(ul_int),  TS(ul_int) },
+  { RS(WRITE_SECTORS),        QS(ul_int),  TS(ul_int) },
+  { RS(WRITE_TIME),           QS(ul_int),  TS(ul_int) },
+  { RS(IO_TIME),              QS(ul_int),  TS(ul_int) },
+  { RS(WEIGHTED_TIME),        QS(ul_int),  TS(ul_int) },
+
+  { RS(IO_INPROGRESS),        QS(s_int),   TS(s_int)  },
+
+  { RS(DELTA_READS),          QS(s_int),   TS(s_int)  },
+  { RS(DELTA_READS_MERGED),   QS(s_int),   TS(s_int)  },
+  { RS(DELTA_READ_SECTORS),   QS(s_int),   TS(s_int)  },
+  { RS(DELTA_READ_TIME),      QS(s_int),   TS(s_int)  },
+  { RS(DELTA_WRITES),         QS(s_int),   TS(s_int)  },
+  { RS(DELTA_WRITES_MERGED),  QS(s_int),   TS(s_int)  },
+  { RS(DELTA_WRITE_SECTORS),  QS(s_int),   TS(s_int)  },
+  { RS(DELTA_WRITE_TIME),     QS(s_int),   TS(s_int)  },
+  { RS(DELTA_IO_TIME),        QS(s_int),   TS(s_int)  },
+  { RS(DELTA_WEIGHTED_TIME),  QS(s_int),   TS(s_int)  },
+};
+
+    /* please note,
+     * this enum MUST be 1 greater than the highest value of any enum */
+enum diskstats_item DISKSTATS_logical_end = MAXTABLE(Item_table);
+
+#undef setNAME
+#undef srtNAME
+#undef RS
+#undef QS
+
+
+// ___ Private Functions ||||||||||||||||||||||||||||||||||||||||||||||||||||||
+// --- dev_node specific support ----------------------------------------------
+
+static struct dev_node *node_add (
+        struct diskstats_info *info,
+        struct dev_node *this)
+{
+    struct dev_node *prev, *walk;
+
+#ifdef ALPHABETIC_NODES
+    if (!info->nodes
+    || (STR_COMPARE(this->name, info->nodes->name) < 0)) {
+        this->next = info->nodes;
+        info->nodes = this;
+        return this;
+    }
+    prev = info->nodes;
+    walk = info->nodes->next;
+    while (walk) {
+        if (STR_COMPARE(this->name, walk->name) < 0)
+            break;
+        prev = walk;
+        walk = walk->next;
+    }
+    prev->next = this;
+    this->next = walk;
+#else
+    if (!info->nodes)
+        info->nodes = this;
+    else {
+        walk = info->nodes;
+        do {
+            prev = walk;
+            walk = walk->next;
+        } while (walk);
+        prev->next = this;
+    }
+#endif
+    return this;
+} // end: node_add
+
+
+static void node_classify (
+        struct dev_node *this)
+{
+    DIR *dirp;
+    struct dirent *dent;
+
+    /* all disks start off as partitions. this function
+       checks /sys/block and changes a device found there
+       into a disk. if /sys/block cannot have the directory
+       read, all devices are then treated as disks. */
+    this->type = DISKSTATS_TYPE_PARTITION;
+
+    if (!(dirp = opendir(SYSBLOCK_DIR))) {
+        this->type = DISKSTATS_TYPE_DISK;
+        return;
+    }
+    while ((dent = readdir(dirp))) {
+        if (strcmp(this->name, dent->d_name) == 0) {
+            this->type = DISKSTATS_TYPE_DISK;
+            break;
+        }
+    }
+    closedir(dirp);
+} // end: node_classify
+
+
+static struct dev_node *node_cut (
+        struct diskstats_info *info,
+        struct dev_node *this)
+{
+    struct dev_node *node = info->nodes;
+
+    if (this) {
+        if (this == node) {
+            info->nodes = node->next;
+            return this;
+        }
+        do {
+            if (this == node->next) {
+                node->next = node->next->next;
+                return this;
+            }
+            node = node->next;
+        } while (node);
+    }
+    return NULL;
+} // end: node_cut
+
+
+static struct dev_node *node_get (
+        struct diskstats_info *info,
+        const char *name)
+{
+    struct dev_node *node = info->nodes;
+
+    while (node) {
+        if (strcmp(name, node->name) == 0)
+            break;
+        node = node->next;
+    }
+    if (node) {
+        /* if this disk or partition has somehow gotten stale, we'll lose
+           it and then pretend it was never actually found ...
+         [ we test against both stamps in case a 'read' was avoided ] */
+        if (node->stamped != info->old_stamp
+        && (node->stamped != info->new_stamp)) {
+            free(node_cut(info, node));
+            node = NULL;
+        }
+    }
+    return node;
+} // end: node_get
+
+
+static int node_update (
+        struct diskstats_info *info,
+        struct dev_node *source)
+{
+    struct dev_node *target = node_get(info, source->name);
+
+    if (!target) {
+        if (!(target = malloc(sizeof(struct dev_node))))
+            return 0;
+        memcpy(target, source, sizeof(struct dev_node));
+        // let's not distort the deltas when a new node is created ...
+        memcpy(&target->old, &target->new, sizeof(struct dev_data));
+        node_classify(target);
+        node_add(info, target);
+        return 1;
+    }
+    // remember history from last time around ...
+    memcpy(&source->old, &target->new, sizeof(struct dev_data));
+    // preserve some stuff from the existing node struct ...
+    source->type = target->type;
+    source->next = target->next;
+    // finally 'update' the existing node struct ...
+    memcpy(target, source, sizeof(struct dev_node));
+    return 1;
+} // end: node_update
+
+
+// ___ Private Functions ||||||||||||||||||||||||||||||||||||||||||||||||||||||
+// --- generalized support ----------------------------------------------------
+
+static inline void diskstats_assign_results (
+        struct diskstats_stack *stack,
+        struct dev_node *node)
+{
+    struct diskstats_result *this = stack->head;
+
+    for (;;) {
+        enum diskstats_item item = this->item;
+        if (item >= DISKSTATS_logical_end)
+            break;
+        Item_table[item].setsfunc(this, node);
+        ++this;
+    }
+    return;
+} // end: diskstats_assign_results
+
+
+static void diskstats_extents_free_all (
+        struct ext_support *this)
+{
+    while (this->extents) {
+        struct stacks_extent *p = this->extents;
+        this->extents = this->extents->next;
+        free(p);
+    };
+} // end: diskstats_extents_free_all
+
+
+static inline struct diskstats_result *diskstats_itemize_stack (
+        struct diskstats_result *p,
+        int depth,
+        enum diskstats_item *items)
+{
+    struct diskstats_result *p_sav = p;
+    int i;
+
+    for (i = 0; i < depth; i++) {
+        p->item = items[i];
+        ++p;
+    }
+    return p_sav;
+} // end: diskstats_itemize_stack
+
+
+static inline int diskstats_items_check_failed (
+        enum diskstats_item *items,
+        int numitems)
+{
+    int i;
+
+    /* if an enum is passed instead of an address of one or more enums, ol' gcc
+     * will silently convert it to an address (possibly NULL).  only clang will
+     * offer any sort of warning like the following:
+     *
+     * warning: incompatible integer to pointer conversion passing 'int' to parameter of type 'enum diskstats_item *'
+     * my_stack = procps_diskstats_select(info, DISKSTATS_noop, num);
+     *                                          ^~~~~~~~~~~~~~~~
+     */
+    if (numitems < 1
+    || (void *)items < (void *)(unsigned long)(2 * DISKSTATS_logical_end))
+        return 1;
+
+    for (i = 0; i < numitems; i++) {
+        // a diskstats_item is currently unsigned, but we'll protect our future
+        if (items[i] < 0)
+            return 1;
+        if (items[i] >= DISKSTATS_logical_end)
+            return 1;
+    }
+
+    return 0;
+} // end: diskstats_items_check_failed
+
+
+/*
+ * diskstats_read_failed:
+ *
+ * @info: info structure created at procps_diskstats_new
+ *
+ * Read the data out of /proc/diskstats putting the information
+ * into the supplied info structure
+ *
+ * Returns: 0 on success, 1 on error
+ */
+static int diskstats_read_failed (
+        struct diskstats_info *info)
+{
+    static const char *fmtstr = "%d %d %" STRINGIFY(DISKSTATS_NAME_LEN) \
+        "s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu";
+    char buf[DISKSTATS_LINE_LEN];
+    struct dev_node node;
+    int rc;
+
+    if (!info->diskstats_fp
+    && (!(info->diskstats_fp = fopen(DISKSTATS_FILE, "r"))))
+        return 1;
+
+    if (fseek(info->diskstats_fp, 0L, SEEK_SET) == -1)
+        return 1;
+
+    info->old_stamp = info->new_stamp;
+    info->new_stamp = time(NULL);
+
+    while (fgets(buf, DISKSTATS_LINE_LEN, info->diskstats_fp)) {
+        // clear out the soon to be 'current'values
+        memset(&node, 0, sizeof(struct dev_node));
+
+        rc = sscanf(buf, fmtstr
+            , &node.major
+            , &node.minor
+            , &node.name[0]
+            , &node.new.reads
+            , &node.new.reads_merged
+            , &node.new.read_sectors
+            , &node.new.read_time
+            , &node.new.writes
+            , &node.new.writes_merged
+            , &node.new.write_sectors
+            , &node.new.write_time
+            , &node.new.io_inprogress
+            , &node.new.io_time
+            , &node.new.io_wtime);
+
+        if (rc != 14) {
+            errno = ERANGE;
+            return 1;
+        }
+        node.stamped = info->new_stamp;
+        if (!node_update(info, &node))
+            return 1;        // here, errno was set to ENOMEM
+    }
+
+    return 0;
+} // end: diskstats_read_failed
+
+
+/*
+ * diskstats_stacks_alloc():
+ *
+ * Allocate and initialize one or more stacks each of which is anchored in an
+ * associated context structure.
+ *
+ * All such stacks will have their result structures properly primed with
+ * 'items', while the result itself will be zeroed.
+ *
+ * Returns a stacks_extent struct anchoring the 'heads' of each new stack.
+ */
+static struct stacks_extent *diskstats_stacks_alloc (
+        struct ext_support *this,
+        int maxstacks)
+{
+    struct stacks_extent *p_blob;
+    struct diskstats_stack **p_vect;
+    struct diskstats_stack *p_head;
+    size_t vect_size, head_size, list_size, blob_size;
+    void *v_head, *v_list;
+    int i;
+
+    vect_size  = sizeof(void *) * maxstacks;                        // size of the addr vectors |
+    vect_size += sizeof(void *);                                    // plus NULL addr delimiter |
+    head_size  = sizeof(struct diskstats_stack);                    // size of that head struct |
+    list_size  = sizeof(struct diskstats_result) * this->numitems;  // any single results stack |
+    blob_size  = sizeof(struct stacks_extent);                      // the extent anchor itself |
+    blob_size += vect_size;                                         // plus room for addr vects |
+    blob_size += head_size * maxstacks;                             // plus room for head thing |
+    blob_size += list_size * maxstacks;                             // plus room for our stacks |
+
+    /* note: all of our memory is allocated in one single blob, facilitating some later free(). |
+             as a minimum, it's important that all of those result structs themselves always be |
+             contiguous within every stack since they will be accessed via a relative position. | */
+    if (NULL == (p_blob = calloc(1, blob_size)))
+        return NULL;
+
+    p_blob->next = this->extents;                                   // push this extent onto... |
+    this->extents = p_blob;                                         // ...some existing extents |
+    p_vect = (void *)p_blob + sizeof(struct stacks_extent);         // prime our vector pointer |
+    p_blob->stacks = p_vect;                                        // set actual vectors start |
+    v_head = (void *)p_vect + vect_size;                            // prime head pointer start |
+    v_list = v_head + (head_size * maxstacks);                      // prime our stacks pointer |
+
+    for (i = 0; i < maxstacks; i++) {
+        p_head = (struct diskstats_stack *)v_head;
+        p_head->head = diskstats_itemize_stack((struct diskstats_result *)v_list, this->numitems, this->items);
+        p_blob->stacks[i] = p_head;
+        v_list += list_size;
+        v_head += head_size;
+    }
+    p_blob->ext_numstacks = maxstacks;
+    return p_blob;
+} // end: diskstats_stacks_alloc
+
+
+static int diskstats_stacks_fetch (
+        struct diskstats_info *info)
+{
+ #define n_alloc  info->fetch.n_alloc
+ #define n_inuse  info->fetch.n_inuse
+ #define n_saved  info->fetch.n_alloc_save
+    struct stacks_extent *ext;
+    struct dev_node *node;
+
+    // initialize stuff -----------------------------------
+    if (!info->fetch.anchor) {
+        if (!(info->fetch.anchor = calloc(sizeof(void *), STACKS_INCR)))
+            return -ENOMEM;
+        n_alloc = STACKS_INCR;
+    }
+    if (!info->fetch_ext.extents) {
+        if (!(ext = diskstats_stacks_alloc(&info->fetch_ext, n_alloc)))
+            return -1;       // here, errno was set to ENOMEM
+        memcpy(info->fetch.anchor, ext->stacks, sizeof(void *) * n_alloc);
+    }
+
+    // iterate stuff --------------------------------------
+    n_inuse = 0;
+    node = info->nodes;
+    while (node) {
+        if (!(n_inuse < n_alloc)) {
+            n_alloc += STACKS_INCR;
+            if ((!(info->fetch.anchor = realloc(info->fetch.anchor, sizeof(void *) * n_alloc)))
+            || (!(ext = diskstats_stacks_alloc(&info->fetch_ext, STACKS_INCR))))
+                return -1;   // here, errno was set to ENOMEM
+            memcpy(info->fetch.anchor + n_inuse, ext->stacks, sizeof(void *) * STACKS_INCR);
+        }
+        diskstats_assign_results(info->fetch.anchor[n_inuse], node);
+        ++n_inuse;
+        node = node->next;
+    }
+
+    // finalize stuff -------------------------------------
+    /* note: we go to this trouble of maintaining a duplicate of the consolidated |
+             extent stacks addresses represented as our 'anchor' since these ptrs |
+             are exposed to a user (um, not that we don't trust 'em or anything). |
+             plus, we can NULL delimit these ptrs which we couldn't do otherwise. | */
+    if (n_saved < n_inuse + 1) {
+        n_saved = n_inuse + 1;
+        if (!(info->fetch.results.stacks = realloc(info->fetch.results.stacks, sizeof(void *) * n_saved)))
+            return -1;
+    }
+    memcpy(info->fetch.results.stacks, info->fetch.anchor, sizeof(void *) * n_inuse);
+    info->fetch.results.stacks[n_inuse] = NULL;
+    info->fetch.results.total = n_inuse;
+
+    return n_inuse;
+ #undef n_alloc
+ #undef n_inuse
+ #undef n_saved
+} // end: diskstats_stacks_fetch
+
+
+static int diskstats_stacks_reconfig_maybe (
+        struct ext_support *this,
+        enum diskstats_item *items,
+        int numitems)
+{
+    if (diskstats_items_check_failed(items, numitems))
+        return -1;
+    /* is this the first time or have things changed since we were last called?
+       if so, gotta' redo all of our stacks stuff ... */
+    if (this->numitems != numitems + 1
+    || memcmp(this->items, items, sizeof(enum diskstats_item) * numitems)) {
+        // allow for our DISKSTATS_logical_end
+        if (!(this->items = realloc(this->items, sizeof(enum diskstats_item) * (numitems + 1))))
+            return -1;       // here, errno was set to ENOMEM
+        memcpy(this->items, items, sizeof(enum diskstats_item) * numitems);
+        this->items[numitems] = DISKSTATS_logical_end;
+        this->numitems = numitems + 1;
+        diskstats_extents_free_all(this);
+        return 1;
+    }
+    return 0;
+} // end: diskstats_stacks_reconfig_maybe
+
+
+// ___ Public Functions |||||||||||||||||||||||||||||||||||||||||||||||||||||||
+
+// --- standard required functions --------------------------------------------
+
+/*
+ * procps_diskstats_new():
+ *
+ * @info: location of returned new structure
+ *
+ * Returns: < 0 on failure, 0 on success along with
+ *          a pointer to a new context struct
+ */
+PROCPS_EXPORT int procps_diskstats_new (
+        struct diskstats_info **info)
+{
+    struct diskstats_info *p;
+
+#ifdef ITEMTABLE_DEBUG
+    int i, failed = 0;
+    for (i = 0; i < MAXTABLE(Item_table); i++) {
+        if (i != Item_table[i].enumnumb) {
+            fprintf(stderr, "%s: enum/table error: Item_table[%d] was %s, but its value is %d\n"
+                , __FILE__, i, Item_table[i].enum2str, Item_table[i].enumnumb);
+            failed = 1;
+        }
+    }
+    if (failed) _Exit(EXIT_FAILURE);
+#endif
+
+    if (info == NULL || *info != NULL)
+        return -EINVAL;
+    if (!(p = calloc(1, sizeof(struct diskstats_info))))
+        return -ENOMEM;
+
+    p->refcount = 1;
+
+    /* do a priming read here for the following potential benefits: |
+         1) ensure there will be no problems with subsequent access |
+         2) make delta results potentially useful, even if 1st time |
+         3) elimnate need for history distortions 1st time 'switch' | */
+    if (diskstats_read_failed(p)) {
+        procps_diskstats_unref(&p);
+        return -errno;
+    }
+
+    *info = p;
+    return 0;
+} // end: procps_diskstats_new
+
+
+PROCPS_EXPORT int procps_diskstats_ref (
+        struct diskstats_info *info)
+{
+    if (info == NULL)
+        return -EINVAL;
+
+    info->refcount++;
+    return info->refcount;
+} // end: procps_diskstats_ref
+
+
+PROCPS_EXPORT int procps_diskstats_unref (
+        struct diskstats_info **info)
+{
+    struct dev_node *node;
+
+    if (info == NULL || *info == NULL)
+        return -EINVAL;
+
+    (*info)->refcount--;
+
+    if ((*info)->refcount < 1) {
+        int errno_sav = errno;
+
+        if ((*info)->diskstats_fp) {
+            fclose((*info)->diskstats_fp);
+            (*info)->diskstats_fp = NULL;
+        }
+        node = (*info)->nodes;
+        while (node) {
+            struct dev_node *p = node;
+            node = p->next;
+            free(p);
+        }
+        if ((*info)->select_ext.extents)
+            diskstats_extents_free_all((&(*info)->select_ext));
+        if ((*info)->select_ext.items)
+            free((*info)->select_ext.items);
+
+        if ((*info)->fetch.anchor)
+            free((*info)->fetch.anchor);
+        if ((*info)->fetch.results.stacks)
+            free((*info)->fetch.results.stacks);
+
+        if ((*info)->fetch_ext.extents)
+            diskstats_extents_free_all(&(*info)->fetch_ext);
+        if ((*info)->fetch_ext.items)
+            free((*info)->fetch_ext.items);
+
+        free(*info);
+        *info = NULL;
+
+        errno = errno_sav;
+        return 0;
+    }
+    return (*info)->refcount;
+} // end: procps_diskstats_unref
+
+
+// --- variable interface functions -------------------------------------------
+
+PROCPS_EXPORT struct diskstats_result *procps_diskstats_get (
+        struct diskstats_info *info,
+        const char *name,
+        enum diskstats_item item)
+{
+    struct dev_node *node;
+    time_t cur_secs;
+
+    errno = EINVAL;
+    if (info == NULL)
+        return NULL;
+    if (item < 0 || item >= DISKSTATS_logical_end)
+        return NULL;
+    errno = 0;
+
+    /* we will NOT read the diskstat file with every call - rather, we'll offer
+       a granularity of 1 second between reads ... */
+    cur_secs = time(NULL);
+    if (1 <= cur_secs - info->new_stamp) {
+        if (diskstats_read_failed(info))
+            return NULL;
+    }
+
+    info->get_this.item = item;
+    //  with 'get', we must NOT honor the usual 'noop' guarantee
+    info->get_this.result.ul_int = 0;
+
+    if (!(node = node_get(info, name))) {
+        errno = ENXIO;
+        return NULL;
+    }
+    Item_table[item].setsfunc(&info->get_this, node);
+
+    return &info->get_this;
+} // end: procps_diskstats_get
+
+
+/* procps_diskstats_reap():
+ *
+ * Harvest all the requested disks information providing
+ * the result stacks along with the total number of harvested.
+ *
+ * Returns: pointer to a diskstats_reaped struct on success, NULL on error.
+ */
+PROCPS_EXPORT struct diskstats_reaped *procps_diskstats_reap (
+        struct diskstats_info *info,
+        enum diskstats_item *items,
+        int numitems)
+{
+    errno = EINVAL;
+    if (info == NULL || items == NULL)
+        return NULL;
+    if (0 > diskstats_stacks_reconfig_maybe(&info->fetch_ext, items, numitems))
+        return NULL;         // here, errno may be overridden with ENOMEM
+    errno = 0;
+
+    if (diskstats_read_failed(info))
+        return NULL;
+    if (0 > diskstats_stacks_fetch(info))
+        return NULL;
+
+    return &info->fetch.results;
+} // end: procps_diskstats_reap
+
+
+/* procps_diskstats_select():
+ *
+ * Obtain all the requested disk/partition information then return
+ * it in a single library provided results stack.
+ *
+ * Returns: pointer to a diskstats_stack struct on success, NULL on error.
+ */
+PROCPS_EXPORT struct diskstats_stack *procps_diskstats_select (
+        struct diskstats_info *info,
+        const char *name,
+        enum diskstats_item *items,
+        int numitems)
+{
+    struct dev_node *node;
+
+    errno = EINVAL;
+    if (info == NULL || items == NULL)
+        return NULL;
+    if (0 > diskstats_stacks_reconfig_maybe(&info->select_ext, items, numitems))
+        return NULL;         // here, errno may be overridden with ENOMEM
+    errno = 0;
+
+    if (!info->select_ext.extents
+    && (!diskstats_stacks_alloc(&info->select_ext, 1)))
+       return NULL;
+
+    if (diskstats_read_failed(info))
+        return NULL;
+    if (!(node = node_get(info, name))) {
+        errno = ENXIO;
+        return NULL;
+    }
+
+    diskstats_assign_results(info->select_ext.extents->stacks[0], node);
+
+    return info->select_ext.extents->stacks[0];
+} // end: procps_diskstats_select
+
+
+/*
+ * procps_diskstats_sort():
+ *
+ * Sort stacks anchored in the passed stack pointers array
+ * based on the designated sort enumerator and specified order.
+ *
+ * Returns those same addresses sorted.
+ *
+ * Note: all of the stacks must be homogeneous (of equal length and content).
+ */
+PROCPS_EXPORT struct diskstats_stack **procps_diskstats_sort (
+        struct diskstats_info *info,
+        struct diskstats_stack *stacks[],
+        int numstacked,
+        enum diskstats_item sortitem,
+        enum diskstats_sort_order order)
+{
+    struct diskstats_result *p;
+    struct sort_parms parms;
+    int offset;
+
+    errno = EINVAL;
+    if (info == NULL || stacks == NULL)
+        return NULL;
+    // a diskstats_item is currently unsigned, but we'll protect our future
+    if (sortitem < 0 || sortitem >= DISKSTATS_logical_end)
+        return NULL;
+    if (order != DISKSTATS_SORT_ASCEND && order != DISKSTATS_SORT_DESCEND)
+        return NULL;
+    if (numstacked < 2)
+        return stacks;
+
+    offset = 0;
+    p = stacks[0]->head;
+    for (;;) {
+        if (p->item == sortitem)
+            break;
+        ++offset;
+        if (p->item >= DISKSTATS_logical_end)
+            return NULL;
+        ++p;
+    }
+    errno = 0;
+
+    parms.offset = offset;
+    parms.order = order;
+
+    qsort_r(stacks, numstacked, sizeof(void *), (QSR_t)Item_table[p->item].sortfunc, &parms);
+    return stacks;
+} // end: procps_diskstats_sort
+
+
+// --- special debugging function(s) ------------------------------------------
+/*
+ *  The following isn't part of the normal programming interface.  Rather,
+ *  it exists to validate result types referenced in application programs.
+ *
+ *  It's used only when:
+ *      1) the 'XTRA_PROCPS_DEBUG' has been defined, or
+ *      2) an #include of 'xtra-procps-debug.h' is used
+ */
+
+PROCPS_EXPORT struct diskstats_result *xtra_diskstats_get (
+        struct diskstats_info *info,
+        const char *name,
+        enum diskstats_item actual_enum,
+        const char *typestr,
+        const char *file,
+        int lineno)
+{
+    struct diskstats_result *r = procps_diskstats_get(info, name, actual_enum);
+
+    if (actual_enum < 0 || actual_enum >= DISKSTATS_logical_end) {
+        fprintf(stderr, "%s line %d: invalid item = %d, type = %s\n"
+            , file, lineno, actual_enum, typestr);
+    }
+    if (r) {
+        char *str = Item_table[r->item].type2str;
+        if (str[0]
+        && (strcmp(typestr, str)))
+            fprintf(stderr, "%s line %d: was %s, expected %s\n", file, lineno, typestr, str);
+    }
+    return r;
+} // end: xtra_diskstats_get_
+
+
+PROCPS_EXPORT struct diskstats_result *xtra_diskstats_val (
+        int relative_enum,
+        const char *typestr,
+        const struct diskstats_stack *stack,
+        struct diskstats_info *info,
+        const char *file,
+        int lineno)
+{
+    char *str;
+    int i;
+
+    for (i = 0; stack->head[i].item < DISKSTATS_logical_end; i++)
+        ;
+    if (relative_enum < 0 || relative_enum >= i) {
+        fprintf(stderr, "%s line %d: invalid relative_enum = %d, valid range = 0-%d\n"
+            , file, lineno, relative_enum, i-1);
+        return NULL;
+    }
+    str = Item_table[stack->head[relative_enum].item].type2str;
+    if (str[0]
+    && (strcmp(typestr, str))) {
+        fprintf(stderr, "%s line %d: was %s, expected %s\n", file, lineno, typestr, str);
+    }
+    return &stack->head[relative_enum];
+    (void)info;
+} // end: xtra_diskstats_val