powercap: add functions to open files

3 files changed, 138 insertions, 0 deletions

diff --git a/RELEASES.md b/RELEASES.md
index ee6443a..4e923bf 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -14,6 +14,10 @@
   * 'powercap_control_type_file_get_path'
   * 'powercap_zone_file_get_path'
   * 'powercap_constraint_file_get_path'
+* Functions to support opening files powercap.h:
+ * 'powercap_control_type_file_open'
+ * 'powercap_zone_file_open'
+ * 'powercap_constraint_file_open'
 
 ### Changed
 
diff --git a/inc/powercap.h b/inc/powercap.h
index 814b296..9e4c0ec 100644
--- a/inc/powercap.h
+++ b/inc/powercap.h
@@ -121,6 +121,7 @@ int powercap_constraint_file_get_name(powercap_constraint_file type, uint32_t co
  * Returns a negative value in case of other error.
  */
 int powercap_get_path(const char* control_type_name, const uint32_t* zones, uint32_t depth, char* buf, size_t size);
+
 /**
  * Get the full path to a control type file.
  * Return is like snprintf, except if the output was truncated due to the size limit, the return value is still > size,
@@ -130,6 +131,7 @@ int powercap_get_path(const char* control_type_name, const uint32_t* zones, uint
  */
 int powercap_control_type_file_get_path(powercap_control_type_file type, const char* control_type_name, char* buf,
                                         size_t size);
+
 /**
  * Get the full path to a zone file.
  * Return is like snprintf, except if the output was truncated due to the size limit, the return value is still > size,
@@ -152,6 +154,31 @@ int powercap_constraint_file_get_path(powercap_constraint_file type, const char*
                                       size_t size);
 
 /**
+ * Open a control type file.
+ * Returns the file descriptor from the open function and assigns it to the powercap_control_type (if not NULL).
+ * Also returns a negative value in case of other errors, like bad parameters.
+ */
+int powercap_control_type_file_open(powercap_control_type* control, powercap_control_type_file type,
+                                    const char* control_type_name, int flags);
+
+/**
+ * Open a zone file.
+ * Returns the file descriptor from the open function and assigns it to the powercap_zone (if not NULL).
+ * Also returns a negative value in case of other errors, like bad parameters.
+ */
+int powercap_zone_file_open(powercap_zone* zone, powercap_zone_file type, const char* control_type_name,
+                            const uint32_t* zones, uint32_t depth, int flags);
+
+/**
+ * Open a constraint file.
+ * Returns the file descriptor from the open function and assigns it to the powercap_constraint (if not NULL).
+ * Also returns a negative value in case of other errors, like bad parameters.
+ */
+int powercap_constraint_file_open(powercap_constraint* constraint, powercap_constraint_file type,
+                                  const char* control_type_name, const uint32_t* zones, uint32_t depth,
+                                  uint32_t constraint_num, int flags);
+
+/**
  * Set the control type's enabled value.
  */
 int powercap_control_type_set_enabled(const powercap_control_type* control, int val);
diff --git a/src/powercap.c b/src/powercap.c
index f1847c3..35ce60e 100644
--- a/src/powercap.c
+++ b/src/powercap.c
@@ -81,6 +81,113 @@ int powercap_constraint_file_get_path(powercap_constraint_file type, const char*
   return snprintf_constraint_file_path(buf, size, control_type_name, zones, depth, constraint, type);
 }
 
+int powercap_control_type_file_open(powercap_control_type* control, powercap_control_type_file type,
+                                    const char* control_type_name, int flags) {
+  char buf[PATH_MAX];
+  int fd;
+  /* check type in case users pass bad int value instead of enum; int cast silences clang compiler */
+  if (!is_valid_control_type(control_type_name) || (int) type < 0 || (int) type > POWERCAP_CONTROL_TYPE_FILE_ENABLED) {
+    errno = EINVAL;
+    return -errno;
+  }
+  fd = open_control_type_file(buf, sizeof(buf), control_type_name, type, flags);
+  if (control) {
+    switch (type) {
+      case POWERCAP_CONTROL_TYPE_FILE_ENABLED:
+        control->enabled = fd;;
+        break;
+      default:
+        // unreachable
+        errno = EINVAL;
+        return -errno;
+    }
+  }
+  return fd;
+}
+
+int powercap_zone_file_open(powercap_zone* zone, powercap_zone_file type, const char* control_type_name,
+                            const uint32_t* zones, uint32_t depth, int flags) {
+  char buf[PATH_MAX];
+  int fd;
+  /* check type in case users pass bad int value instead of enum; int cast silences clang compiler */
+  if (!is_valid_control_type(control_type_name) || (int) type < 0 || (int) type > POWERCAP_ZONE_FILE_NAME ||
+      (depth && !zones)) {
+    errno = EINVAL;
+    return -errno;
+  }
+  fd = open_zone_file(buf, sizeof(buf), control_type_name, zones, depth, type, flags);
+  if (zone) {
+    switch (type) {
+      case POWERCAP_ZONE_FILE_MAX_ENERGY_RANGE_UJ:
+        zone->max_energy_range_uj = fd;
+        break;
+      case POWERCAP_ZONE_FILE_ENERGY_UJ:
+        zone->energy_uj = fd;
+        break;
+      case POWERCAP_ZONE_FILE_MAX_POWER_RANGE_UW:
+        zone->max_power_range_uw = fd;
+        break;
+      case POWERCAP_ZONE_FILE_POWER_UW:
+        zone->power_uw = fd;
+        break;
+      case POWERCAP_ZONE_FILE_ENABLED:
+        zone->enabled = fd;
+        break;
+      case POWERCAP_ZONE_FILE_NAME:
+        zone->name = fd;
+        break;
+      default:
+        // unreachable
+        errno = EINVAL;
+        return -errno;
+    }
+  }
+  return fd;
+}
+
+int powercap_constraint_file_open(powercap_constraint* constraint, powercap_constraint_file type,
+                                  const char* control_type_name, const uint32_t* zones, uint32_t depth,
+                                  uint32_t constraint_num, int flags) {
+  char buf[PATH_MAX];
+  int fd;
+  if (!constraint || !is_valid_control_type(control_type_name) ||
+      (int) type < 0 || (int) type > POWERCAP_CONSTRAINT_FILE_NAME || (depth && !zones)) {
+    errno = EINVAL;
+    return -errno;
+  }
+  fd = open_constraint_file(buf, sizeof(buf), control_type_name, zones, depth, constraint_num, type, flags);
+  if (constraint) {
+    switch (type) {
+      case POWERCAP_CONSTRAINT_FILE_POWER_LIMIT_UW:
+        constraint->power_limit_uw = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_TIME_WINDOW_US:
+        constraint->time_window_us = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_MAX_POWER_UW:
+        constraint->max_power_uw = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_MIN_POWER_UW:
+        constraint->min_power_uw = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_MAX_TIME_WINDOW_US:
+        constraint->max_time_window_us = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_MIN_TIME_WINDOW_US:
+        constraint->min_time_window_us = fd;
+        break;
+      case POWERCAP_CONSTRAINT_FILE_NAME:
+        constraint->name = fd;
+        break;
+      default:
+        // unreachable
+        errno = EINVAL;
+        return -errno;
+    }
+  }
+  return fd;
+}
+
 #define VERIFY_ARG(arg) \
   if (!(arg)) { \
     errno = EINVAL; \