postgres/src/bin/psql/variables.c

/*
 * 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;
}