variables.c

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/*
 * psql - the PostgreSQL interactive terminal
 *
 * Copyright (c) 2000-2016, PostgreSQL Global Development Group
 *
 * src/bin/psql/variables.c
 */
#include "postgres_fe.h"

#include "common.h"
#include "variables.h"


/*
 * Check whether a variable's name is allowed.
 *
 * We allow any non-ASCII character, as well as ASCII letters, digits, and
 * underscore.  Keep this in sync with the definition of variable_char in
 * psqlscan.l and psqlscanslash.l.
 */
static bool
valid_variable_name(const char *name)
{
    const unsigned char *ptr = (const unsigned char *) name;

    /* Mustn't be zero-length */
    if (*ptr == '\0')
        return false;

    while (*ptr)
    {
        if (IS_HIGHBIT_SET(*ptr) ||
            strchr("ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz"
                   "_0123456789", *ptr) != NULL)
            ptr++;
        else
            return false;
    }

    return true;
}

/*
 * A "variable space" is represented by an otherwise-unused struct _variable
 * that serves as list header.
 */
VariableSpace
CreateVariableSpace(void)
{
    struct _variable *ptr;

    ptr = pg_malloc(sizeof *ptr);
    ptr->name = NULL;
    ptr->value = NULL;
    ptr->assign_hook = NULL;
    ptr->next = NULL;

    return ptr;
}

const char *
GetVariable(VariableSpace space, const char *name)
{
    struct _variable *current;

    if (!space)
        return NULL;

    for (current = space->next; current; current = current->next)
    {
        if (strcmp(current->name, name) == 0)
        {
            /* this is correct answer when value is NULL, too */
            return current->value;
        }
    }

    return NULL;
}

/*
 * Try to interpret "value" as boolean value.
 *
 * Valid values are: true, false, yes, no, on, off, 1, 0; as well as unique
 * prefixes thereof.
 *
 * "name" is the name of the variable we're assigning to, to use in error
 * report if any.  Pass name == NULL to suppress the error report.
 */
bool
ParseVariableBool(const char *value, const char *name)
{
    size_t      len;

    if (value == NULL)
        return false;           /* not set -> assume "off" */

    len = strlen(value);

    if (pg_strncasecmp(value, "true", len) == 0)
        return true;
    else if (pg_strncasecmp(value, "false", len) == 0)
        return false;
    else if (pg_strncasecmp(value, "yes", len) == 0)
        return true;
    else if (pg_strncasecmp(value, "no", len) == 0)
        return false;
    /* 'o' is not unique enough */
    else if (pg_strncasecmp(value, "on", (len > 2 ? len : 2)) == 0)
        return true;
    else if (pg_strncasecmp(value, "off", (len > 2 ? len : 2)) == 0)
        return false;
    else if (pg_strcasecmp(value, "1") == 0)
        return true;
    else if (pg_strcasecmp(value, "0") == 0)
        return false;
    else
    {
        /* NULL is treated as false, so a non-matching value is 'true' */
        if (name)
            psql_error("unrecognized value \"%s\" for \"%s\"; assuming \"%s\"\n",
                       value, name, "on");
        return true;
    }
}


/*
 * Read numeric variable, or defaultval if it is not set, or faultval if its
 * value is not a valid numeric string.  If allowtrail is false, this will
 * include the case where there are trailing characters after the number.
 */
int
ParseVariableNum(const char *val,
                 int defaultval,
                 int faultval,
                 bool allowtrail)
{
    int         result;

    if (!val)
        result = defaultval;
    else if (!val[0])
        result = faultval;
    else
    {
        char       *end;

        result = strtol(val, &end, 0);
        if (!allowtrail && *end)
            result = faultval;
    }

    return result;
}

int
GetVariableNum(VariableSpace space,
               const char *name,
               int defaultval,
               int faultval,
               bool allowtrail)
{
    const char *val;

    val = GetVariable(space, name);
    return ParseVariableNum(val, defaultval, faultval, allowtrail);
}

void
PrintVariables(VariableSpace space)
{
    struct _variable *ptr;

    if (!space)
        return;

    for (ptr = space->next; ptr; ptr = ptr->next)
    {
        if (ptr->value)
            printf("%s = '%s'\n", ptr->name, ptr->value);
        if (cancel_pressed)
            break;
    }
}

bool
SetVariable(VariableSpace space, const char *name, const char *value)
{
    struct _variable *current,
               *previous;

    if (!space)
        return false;

    if (!valid_variable_name(name))
        return false;

    if (!value)
        return DeleteVariable(space, name);

    for (previous = space, current = space->next;
         current;
         previous = current, current = current->next)
    {
        if (strcmp(current->name, name) == 0)
        {
            /* found entry, so update */
            if (current->value)
                free(current->value);
            current->value = pg_strdup(value);
            if (current->assign_hook)
                (*current->assign_hook) (current->value);
            return true;
        }
    }

    /* not present, make new entry */
    current = pg_malloc(sizeof *current);
    current->name = pg_strdup(name);
    current->value = pg_strdup(value);
    current->assign_hook = NULL;
    current->next = NULL;
    previous->next = current;
    return true;
}

/*
 * This both sets a hook function, and calls it on the current value (if any)
 */
bool
SetVariableAssignHook(VariableSpace space, const char *name, VariableAssignHook hook)
{
    struct _variable *current,
               *previous;

    if (!space)
        return false;

    if (!valid_variable_name(name))
        return false;

    for (previous = space, current = space->next;
         current;
         previous = current, current = current->next)
    {
        if (strcmp(current->name, name) == 0)
        {
            /* found entry, so update */
            current->assign_hook = hook;
            (*hook) (current->value);
            return true;
        }
    }

    /* not present, make new entry */
    current = pg_malloc(sizeof *current);
    current->name = pg_strdup(name);
    current->value = NULL;
    current->assign_hook = hook;
    current->next = NULL;
    previous->next = current;
    (*hook) (NULL);
    return true;
}

bool
SetVariableBool(VariableSpace space, const char *name)
{
    return SetVariable(space, name, "on");
}

bool
DeleteVariable(VariableSpace space, const char *name)
{
    struct _variable *current,
               *previous;

    if (!space)
        return false;

    for (previous = space, current = space->next;
         current;
         previous = current, current = current->next)
    {
        if (strcmp(current->name, name) == 0)
        {
            if (current->value)
                free(current->value);
            current->value = NULL;
            /* Physically delete only if no hook function to remember */
            if (current->assign_hook)
                (*current->assign_hook) (NULL);
            else
            {
                previous->next = current->next;
                free(current->name);
                free(current);
            }
            return true;
        }
    }

    return true;
}